JVM warm up by Escape Analysis
Why JVM need warm up
I don’t know how and why you get to this blog. But I know the key words in your mind are “warm” for JVM. As the name “warm up” suggested, and like what you normally do before work out. Warm up means get your body/system ready and tune it to perfect state As for systems running under JVM, if they are time critical and latency sensitive. The best approach to make it run in good state is good preparation.
One feasible strategy for low-latency applications, we need to cache all classes beforehand – so that they’re available instantly when accessed at runtime.
This process of tuning the JVM is known as warming up.
There are multiple tools & approach to implement warm up, while I’m going to dig into one of most important strategy to warm up your application in JVM. That’s EA: Escape Analysis.
Escape Analysis
Java objects are created and stored in the heap. The programming language does not offer the possibility to let the programmer decide if an object should be generated in the stack. But in certain cases it would be desirable to allocate an object on the stack, as the memory allocation on the stack is cheaper than the memory allocation in the heap, deallocation on the stack is free and the stack is efficiently managed by the runtime.
The JVM uses therefore internally escape analysis to check if an object is used only with a thread or method. If the JVM identify this it may decide to create the object on the stack, increasing performance of the Java program.
Escape analysis is a technique by which the Java Hotspot Server Compiler can analyze the scope of a new object’s uses and decide whether to allocate it on the Java heap.
Why EA help to boost application performance in JVM?
As you know, JVM will allocate memory space in different sections. They performs significanlty different, normally heap is slower than stack, which is even slower than CPU registers. So to improve system performance, we’d put our data step away from heap. When your java source code being compiled, JIT will leverage Escape Analysis to allocate space on the method stack or even in CPU registers instead of Java heap space. This is a very important performance optimization because stack allocation and de-allocation are much faster than heap space allocation.
How escape analysis work
Based on escape analysis during JIT, an object’s escape state might be one of the following:
- GlobalEscape – An object escapes the method and thread. For example, an object stored in a static field, or, stored in a field of an escaped object, or, returned as the result of the current method.
- ArgEscape – An object passed as an argument or referenced by an argument but does not globally escape during a call. This state is determined by analyzing the bytecode of called method.
- NoEscape – A scalar replaceable object, meaning its allocation could be removed from generated code.
After escape analysis, the server compiler eliminates scalar replaceable object allocations and associated locks from generated code. The server compiler also eliminates locks for all non-globally escaping objects.
Please beadvised it does not replace a heap allocation with a stack allocation for non-globally escaping objects.
JIT inline optimisation
The JIT aggressively inlines methods, removing the overhead of method calls. Methods that can be inlined include static, private or final methods but also public methods if it can be determined that they are not overridden.
Because of this, subsequent class loading can invalidate the previously generated code. Because inlining every method everywhere would take time and would generate an unreasonably big binary, the JIT compiler inlines the hot methods first until it reaches a threshold. To determine which methods are hot, the JVM keeps counters to see how many times a method is called and how many loop iterations it has executed. This means that inlining happens only after a steady state has been reached, so you need to repeat the operations a certain number of times before there is enough profiling information available for the JIT compiler to do its job.
Rather than trying to guess what the JIT is doing, you can take a peek at what’s happening by turning on java command line flags: -XX:+PrintCompilation -XX:+UnlockDiagnosticVMOptions -XX:+PrintInlining
Here is what they do:
-XX:+PrintCompilation: logs when JIT compilation happens
-XX:+UnlockDiagnosticVMOptions: enables other flags like -XX:+PrintInlining
Improve performance by removing locking
As you konw, Lock would significantely slow down or even freeze your application running in JVM.
During Escape analysis. GlobalEscape and ArgEscape objects must be allocated on the heap, but for ArgEscape objects it is possible to remove some locking and memory synchronization overhead because these objects are only visible from the calling thread.
The NoEscape objects may be allocated freely, for example on the stack instead of on the heap. In fact, under some circumstances, it is not even necessary to construct an object at all, but instead only the object’s scalar values, such as an int for the object Integer. Synchronization may be removed too, because we know that only this thread will use the objects. For example, if we were to use the somewhat ancient StringBuffer (which as opposed to StringBuilder has synchronized methods), then these synchronizations could safely be removed.
EA is currently only available under the C2 HotSpot Compiler so we have to make sure that we run in -server mode.
Why It Matters
In theory, NoEscape objects objects can be allocated on the stack or even in CPU registers using EA, giving very fast execution.
When we allocate objects on the heap, we start to drain our CPU caches because objects are placed on different addresses on the heap possibly far away from each other. This way we will quickly deplete our L1 CPU cache and performance will decrease. With EA and stack allocation on the other hand, we are using memory that (most likely) is already in the L1 cache anyhow. So, EA and stack allocation will improve our localization of data. This is good from a performance standpoint.
Obviously, the garbage collects needs to run much less frequently when we are using EA with stack allocation. This is perhaps the biggest performance advantage. Recall that each time the JVM runs a complete heap scan, we take performance out of our CPUs and the CPU caches will quickly deplete. Not to mention if we have virtual memory paged out on our server, whereby GC is devastating for performance.
The most important advantage of EA is not performance though. EA allows us to use local abstractions like Lambdas, Functions, Streams, Iterators etc. without any significant performance penalty so that we can write better and more readable code. Code that describes what we are doing rather than how it is done.
The GC cleans up the heap and not the stack. The stack is cleaned up automatically when methods return to their caller whereby the stack pointer is reset to its former value. So GC will clean up objects that ended up on the stack before EA/C2 compilation could be performed. The actual instances (or rather their corresponding representations) live on the stack, there are no referenced objects on the stack in the context of EA optimizations.
JIT optimization
Some JIT Compilation Techniques
One of the most common JIT compilation techniques used by Java HotSpot VM is inlining, which is the practice of substituting the body of a method into the places where that method is called. Inlining saves the cost of calling the method; no new stack frames need to be created. By default, Java HotSpot VM will try to inline methods that contain less than 35 bytes of JVM bytecode.
Another common optimization that Java HotSpot VM makes is monomorphic dispatch, which relies on the observed fact that, usually, there aren’t paths through a method that cause an object reference to be of one type most of the time but of another type at other times.
You might think that having different types via different code paths would be ruled out by Java’s static typing, but remember that an instance of a subtype is always a valid instance of a supertype (this principle is known as the Liskov substitution principle, after Barbara Liskov). This situation means that there could be two paths into a method—for example, one that passes an instance of a supertype and one that passes an instance of a subtype—which would be legal by the rules of Java’s static typing (and does occur in practice).
In the usual case (the monomorphic case), however, having different, path-dependent types does not happen. So we know the exact method definitions that will be called when methods are called on the passed object, because we don’t need to check which override is actually being used. This means we can eliminate the overhead of doing virtual method lookup, so the JIT compiler can emit optimized machine code that is often faster than an equivalent C++ call (because in the C++ case, the virtual lookup cannot easily be eliminated). The two Java HotSpot VM compiler modes use different techniques for JIT compilation, and they can output very different machine code for the same Java method. Modern Java applications, however, can usually make use of both compilation modes.
Java HotSpot VM uses many other techniques to optimize the code that JIT compilation produces. Loop optimization, type sharpening, dead-code elimination, and intrinsics are just some of the other ways that Java HotSpot VM tries to optimize code as much as it can. Techniques are frequently layered one on top of another, so that once one optimization has been applied, the compiler might be able to see more optimizations that can be performed.
Compilation Modes
Inside Java HotSpot VM, there are actually two separate JIT compiler modes, which are known as C1 and C2. C1 is used for applications where quick startup and rock-solid optimization are required; GUI applications are often good candidates for this compiler. C2, on the other hand, was originally intended for long-running, predominantly server-side applications. Prior to some of the later Java SE 7 releases, these two modes were available using the -client and -server switches, respectively.
The two compiler modes use different techniques for JIT compilation, and they can output very different machine code for the same Java method. Modern Java applications, however, can usually make use of both compilation modes. To take advantage of this fact, starting with some of the later Java SE 7 releases, a new feature called tiered compilation became available. This feature uses the C1 compiler mode at the start to provide better startup performance. Once the application is properly warmed up, the C2 compiler mode takes over to provide more-aggressive optimizations and, usually, better performance. With the arrival of Java SE 8, tiered compilation is now the default behavior.
Java memory monitoring tools
pemi$ jps | grep Main
50903 Main
pemi$ jmap -histo 50903 | head
num #instances #bytes class name
----------------------------------------------
1: 95 42952184 [I
2: 1079 101120 [C
3: 485 55272 java.lang.Class
4: 526 25936 [Ljava.lang.Object;
5: 13 25664 [B
6: 1057 25368 java.lang.String
7: 74 5328 java.lang.reflect.Field
jmap - Memory Map
Tool or Option Description and Usage
Java Mission Control
Java Mission Control (JMC) is a new JDK profiling and diagnostic tools platform for HotSpot JVM. It s a tool suite basic monitoring, managing, and production time profiling and diagnostics with high performance. Java Mission Control minimizes the performance overhead that’s usually an issue with profiling tools. See Java Mission Control.
jcmd utility
The jcmd utility is used to send diagnostic command requests to the JVM, where these requests are useful for controlling Java Flight Recordings. The JFRs are used to troubleshoot and diagnose JVM and Java Applications with flight recording events. See The jcmd Utility.
Java VisualVM
This utility provides a visual interface for viewing detailed information about Java applications while they are running on a Java Virtual Machine. This information can be used in troubleshooting local and remote applications, as well as for profiling local applications. See Java VisualVM.
JConsole utility
This utility is a monitoring tool that is based on Java Management Extensions (JMX). The tool uses the built-in JMX instrumentation in the Java Virtual Machine to provide information about performance and resource consumption of running applications. See JConsole.
jmap utility
This utility can obtain memory map information, including a heap histogram, from a Java process, a core file, or a remote debug server. See The jmap Utility.
jps utility
This utility lists the instrumented Java HotSpot VMs on the target system. The utility is very useful in environments where the VM is embedded, that is, it is started using the JNI Invocation API rather than the java launcher. See The jps Utility.
jstack utility
This utility can obtain Java and native stack information from a Java process. On Oracle Solaris and Linux operating systems the utility can alos get the information from a core file or a remote debug server. See The jstack Utility.
jstat utility
This utility uses the built-in instrumentation in Java to provide information about performance and resource consumption of running applications. The tool can be used when diagnosing performance issues, especially those related to heap sizing and garbage collection. See The jstat Utility.
jstatd daemon
This tool is a Remote Method Invocation (RMI) server application that monitors the creation and termination of instrumented Java Virtual Machines and provides an interface to allow remote monitoring tools to attach to VMs running on the local host. See The jstatd Daemon.
visualgc utility
This utility provides a graphical view of the garbage collection system. As with jstat, it uses the built-in instrumentation of Java HotSpot VM. See The visualgc Tool.
Native tools
Each operating system has native tools and utilities that can be useful for monitoring purposes. For example, the dynamic tracing (DTrace) capability introduced in Oracle Solaris 10 operating system performs advanced monitoring. See Native Operating System Tools.
$ jps
16217 MyApplication
16342 jps
The utility lists the virtual machines for which the user has access rights. This is determined by access-control mechanisms specific to the operating system. On Oracle Solaris operating system, for example, if a non-root user executes the jps utility, then the output is a list of the virtual machines that were started with that user's uid.
In addition to listing the PID, the utility provides options to output the arguments passed to the application's main method, the complete list of VM arguments, and the full package name of the application's main class. The jps utility can also list processes on a remote system if the remote system is running the jstatd daemon.
GC-less Java
Java Development without GC All products developed by Coral Blocks have the very important feature of leaving ZERO garbage behind. Because the latency imposed by the Java Garbage Collector (i.e. GC) is unacceptable for high-performance systems and because it is impossible to turn off the GC, the best option for real-time systems in Java is to not produce any garbage at all so that the GC never kicks in. Imagine a high-performance matching engine operating in the microsecond level, sending and receiving hundreds of thousands messages per second. If at any given time the GC decides to kick in with its 1+ millisecond latencies, the disruption in the system will be huge. Therefore, if you want to develop real-time systems in Java with minimal variance and latency, the best option is to do it right without creating any garbage for the GC.
Warming up, Checking the GC and Sampling
The key to make sure your system is not creating any garbage is to warm up your critical path from start to finish a couple of million times and then check for memory allocation another couple of million times. If it is allocating memory linearly as the number of iterations increases, it is most likely creating garbage and you should use the stack trace
2024
Awesome-awk-tools Simplicity is the ultimate sophistication
“Simplicity is the ultimate sophistication.” - Leonardo da Vinci
When Your Retry Mechanism Doesn’t Retry - A Tale of String Matching Gone Wrong
The biggest room in the world is the room for improvement. — Helmut Schmidt
Avoiding Data Loss - S3 Lifecycle Rules During Terraform Version Migrations
Your past is a lesson. Not a life sentence. Forgive yourself and focus on the future. -Mel Robbins
The Great Migration – Moving Azure Web App and App Service Plan Across Subscriptions
A younger brother knows his older brother better than anyone else.
awesome mr W
You are not a drop in the ocean, you are the entire ocean in a drop.
Mastering Date Formatting in Bash: A Developer’s Guide
A younger brother knows his older brother better than anyone else.
Kubenetes Zero to Hero
You are not a drop in the ocean, you are the entire ocean in a drop.
Unraveling The Mystery Nested Sql Comments In Vscode
Unraveling the Mystery of Nested SQL Comments in VS Code Have you ever found yourself staring at a sea of incorrectly highlighted SQL code in Visual Studio C...
Flyway Self Healing
how to let your flyway database scheme migrate more robustly and self healing
Flyway Self Healing
how to let your flyway database scheme migrate more robustly and self healing
Lock Wait Timeout Exceptions and Data Persistence Issues in Spring Boot and Hibernate
If you can make your hobby your profession, you never have to work another day in your life. —Anonymous
Unlocking SQL Superpowers-> How CTEs Will Transform Your Database Queries
“Stress is like a pulse, if you have it you are alive.” — Steve Maraboli
Why Hibernate Still Logs SQL Even When Disabled in application.yaml
Good leadership consists of doing less and being more. —Dave Ramsey
The Curious Case of Azure Key Vault Defender Alerts - When Security Settings Play Hide and Seek
A leader takes people where they want to go. A great leader takes people where they don’t necessarily want to go, but ought to be. —Rosalynn Carter, forme...
Streamline Your Workflow by Fastest way to run Maven Builds with a Keyboard Shortcut in IntelliJ
A leader takes people where they want to go. A great leader takes people where they don’t necessarily want to go, but ought to be. —Rosalynn Carter, forme...
使用 c3p0 连接池解决 Spring Boot 中断的数据库连接问题（解决 Spring Boot 中断的数据库连接问题）
一旦你知道答案，一切都会变得简单。” —— 戴夫·梅吉（Dave Magee）
Resolving Disconnected Database Connections in Spring Boot with c3p0 Connection Pool
“Everything is easy, once you know the answer. —Dave Magee
IntelliJ sudden crashed of compile error MapStruct or Kotlin
Life begins at the edge of the comfort zone
Deep dive for word press preview nonce
One must learn by doing the thing; for though you think you know it, you have no certainty, until you try. —Sophocles
你不了解的word press 的 preview nonce
One must learn by doing the thing; for though you think you know it, you have no certainty, until you try. —Sophocles
Notes and pitfalls for redis development
A younger brother knows his older brother better than anyone else.
2023
Awesome Jq For Coders
Mastering JSON Data Manipulation with jq: A Comprehensive Guide
Awesome Xlookup Over Vlookup
XLOOKUP vs. VLOOKUP: Excel’s Dynamic Duo for Data Lookup
Ports Discovery On Hosts
To find out the port numbers running in servers
Troubleshoot Mariadb In Linux
The simplest way to check an mariadb is runnning systemctl status mariadb
Az Cli
To run commands in VMs in Azure
From filter to CNN (Convolutional Network)
The biggest room in the world is the room for improvement. Filters in Convolutional Neural Networks (CNNs) In the context of convolutional neural net...
Unlocking Network Secrets A MacBook Traceroute Tutorial
A younger brother knows his older brother better than anyone else.
How to Test Logging Output in JUnit
A younger brother knows his older brother better than anyone else.
Cheap and flexible computing
whether it seems possible or not - go for it Cheaper X 2 to EC2, to use Fargate Spot With Fargate Spot you can run interruption tolerant Amazon ECS t...
How Guru to use Capturing Groups in Python Regular Expressions
A dream deferred is a dream denied. -Langston Hughes
Composition and Aggregation in Object-Oriented Modeling
“The past does not equal the future unless you live there.” - Tony Robbins
Exploring the useRequest Hook from ahooks
“The best way to predict the future is to invent it.” - Alan Kay
Understanding Python’s Late Binding Behavior A Deep Dive
“Hang Out with People Who are Better than You.” — Warren Buffett
Understanding React export a Component
A young idler, an old beggar. - William Shakespeare Understanding React export a Component In this blog post, we will dive into the code of the RepoU...
why use mid = (low + high) // 2 but not (high-low)//2
“Don’t let yesterday take up too much of today.” - Will Rogers
Introduction to Generator Expressions in Python
“It always seems impossible until it’s done.” - Nelson Mandela
Introduction to Generator Expressions in Python
We never lose friends but just start to find real ones. - William Shakespeare
The Curious Case of ‘localhost’ vs ‘127.0.0.1’ in MySQL Connections
Everybody may not to be famous but everybody can be great. “The Curious Case of ‘localhost’ vs ‘127.0.0.1’ in MySQL Connections” Have you ever encoun...
Understanding Backpropagation in Neural Networks
Your past is a lesson. Not a life sentence. Forgive yourself and focus on the future. -Mel Robbins
Understanding Backpropagation in Neural Networks
Your past is a lesson. Not a life sentence. Forgive yourself and focus on the future. -Mel Robbins
Understanding Confusion Matrix in WEKA
Your past is a lesson. Not a life sentence. Forgive yourself and focus on the future. -Mel Robbins
Useful Shortcut Tips for MacBook Office Workers
A young idler, an old beggar. - William Shakespeare
Understanding d-Separation in Graphical Models
A young idler, an old beggar. - William Shakespeare
How To Split Sql Insert Statement
“Don’t let yesterday take up too much of today.” - Will Rogers
docker-commands-bible
“Don’t let yesterday take up too much of today.” - Will Rogers
Adversarial Search: Unleashing The Power Of AI In Competitive Games
“What you seek is seeking you.” — Rumi
Weird Problem Changed Configurations In Pom Xml Not Work
“I can’t relate to lazy people. We don’t speak the same language.” — Kobe Bryant
AI Basics, Talk About Searches
“What you seek is seeking you.” — Rumi
Xpath Playground Best Practices
A young idler, an old beggar. - William Shakespeare
UUID deep dive
A young idler, an old beggar. - William Shakespeare
Compile Error Java Kotlin Coexist Project In Intellij
The biggest room in the world is the room for improvement. — Helmut Schmidt
Who Is Running On Port 8080
A young idler, an old beggar. - William Shakespeare
Let AI To Manage Stripe Payment
A young idler, an old beggar. - William Shakespeare
RestTemplate Powered Http2
Why HTTP/2 is Better
Compile Error Java Kotlin Coexist Project In Intellij
How to Fine Tune RestTemplate
how-to-travel-in-cairns
大堡礁的一些知识
Compile Error Java Kotlin Coexist Project In Intellij
The root cause is your customized HttpMessageConverter stopped processing of WebSecurity
io_mockk_MockKException__no_answer_found_for
A young idler, an old beggar. - William Shakespeare
which-port-my-service-is-running
Summary As a Java developer, it’s important to know how to find out which port number your Spring service is running on. This information is useful when you ...
How To Install Sonarqube Via Docker
“Hang Out with People Who are Better than You.” — Warren Buffett
how-to-auto-login-for-citrix-receiver-vpn-client
“Hang Out with People Who are Better than You.” — Warren Buffett
pip-install-behind-proxy
Failure of timeout or connection when running pip install
Elk Search Tips
message:/'Invoking SP with quoteContext*werqewr-1234asdf-sdf23-9d83-asdf23*'/
what is StrictHostKeyChecking in ssh
What’s and how to avoid error of the authenticity of host ‘xxx’ can’t be established You can suppress the “The authenticity of host ‘’ can’t be established” ...
know in and out of free command
You are not a drop in the ocean, you are the entire ocean in a drop.
Chinese Verb
知其雄，守其雌 什么意思
Deep dive for errors during Spring Boot Tests
Transaction silently rolled back because it has been marked as rollback-only
Is Import Star Devil
Why using wildcard import is devil
How To Run Testing Multiple Threading
A sample to test concurrent JPA modifications
Stress Test Concurrency Jpa Entity Random Update
A runnable example in Java to create a cucumber test code files to simulate multiple read and write entity via JPA repository
How To Use Aop Test Utils.jpg
What’s purpose of AopTestUtils.getTargetObject()?
A Brief Introduction To Lookbehind And Lookahead In Regular Expressions
“The only way to do great work is to love what you do.” - Steve Jobs
master-spring-properties-injection
“The only way to do great work is to love what you do.” - Steve Jobs
Transaction Commit In Hibernate Jpa
Give me sample to test concurrent JPA modifications
Spring Boot Test In A Nutshell
what’s spring boot test annotation
How To Detach In Jpa
A real sample of using JPA detach
Feature Flag Spring Boot
summary Feature flag library in spring boot
What’s Difference Of Cny And Cnh
what’s difference of CNY and CNH CNY and CNH are both currencies used in China, but they are different in a few important ways:
Hibernate Transaction Management
Details of how hibernate transaction management works
Spring Cloud Masterpiece 10
In spring cloud what’s when to use feign client and when to sue resttemplate
Spring Cloud Master Piece 9
What’s spring cloud config Spring Cloud Config is a distributed configuration server that provides a centralized location to manage external properties for a...
Spring API Gateway Best Practices
Spring API Gateway Best Practices
Splitting A Monolithic Application Into Microservices
Splitting a monolithic application into microservices can be a complex process that requires careful planning and implementation. Here is a high-level approa...
Spring Cloud Master Piece 6
Sample me build a micro service payment system with spring cloud Here’s an example of building a microservice payment system using Spring Cloud:
Difference Between Using Ribbon And A Load Balancer
The main difference between using Ribbon and a Load Balancer is the location of the load balancing logic.
Spring Cloud Master Piece 5
How to add security among micro service in spring boot
Spring Cloud Master Piece 4
How to use service discovery in spring book
Spring Cloud Master Piece 3
Sample me how to build a eureka service discovery
Spring Cloud Master Piece 2
what’s usage of bootstrap yml In a Spring Boot application, the bootstrap.yml (or bootstrap.properties) file is used for configuring the application’s enviro...
Spring Cloud Master Piece 1
what’s API gateway An API Gateway is a key component in microservices architecture that acts as a single entry point for client requests to a microservices-b...
annoying-debug-logs-in-springboot-test
Stop annoying debug logs in spring boot test
how-to-stop-quartz-scheduling-during-springboot-test
how-to-stop-quartz-scheduling-during-springboot-test
Date Is The Most Ignored Treasure In Macbook
“The only way to do great work is to love what you do.” - Steve Jobs
Mysql Operator To Extract Json
“Believe you can and you’re halfway there.” - Theodore Roosevelt
Master Microfrontends
“The only way to do great work is to love what you do.” - Steve Jobs
How To Convert One Monolith Java System To Microservices
Whatever is worth doing is worth doing well.
How To Config JFR Java Flight Control
“Climb the mountains and get their good tidings. Nature’s peace will flow into you as sunshine flows into trees. The winds will blow their own freshness i...
How To Read Jdk Mission Control Report
Live the life you’ve imagined.
Jdk Mission Control Can Not Start In Macbook M1
“Climb the mountains and get their good tidings. Nature’s peace will flow into you as sunshine flows into trees. The winds will blow their own freshness i...
How To Keep Multiple Copy Paste Value In Macbook
“Winning is nice if you don’t lose your integrity in the process.” — Arnold Horshak
Google マップ内の写真のコメントが表示されない
紹介 私は、私のOppo Androidスマートフォンのアプリ「Googleマップ」で奇妙な問題が発生していることに気づきました。Googleマップで特定の場所（例えば「中央公園」）を検索すると、通常、このアプリは公園の写真やコメントリストを表示するはずです。例えば、誰かが公園の芝生や川の写真を投稿し、便利な場所...
Les commentaires des photos ne s’affichent pas dans Google Maps.
Introduction J’ai remarqué un problème étrange avec l’application “Google Maps” de mon téléphone Android Oppo. Lorsque vous recherchez un lieu sur Google Map...
Is Kerberos One Ssl/tls?
Nothing is as easy as it looks.
How To Save Expect Script Run Output To File Locally
Nothing is as easy as it looks.
Refind Java Concurrency
You are not a drop in the ocean, you are the entire ocean in a drop.
Refind Java Solid Principles
You are not a drop in the ocean, you are the entire ocean in a drop.
How To Extract Table Name From Sql By Python
You are not a drop in the ocean, you are the entire ocean in a drop.
How to find non-empty json value in mysql
You are not a drop in the ocean, you are the entire ocean in a drop.
master-cglib-in-java
You are not a drop in the ocean, you are the entire ocean in a drop.
What is shape function in python pandas
An honest days’ work makes for a good night’s sleep.
What is shape function in python pandas
Imagination is the key ingredient to a happy life.
What is default logic in python try except else
Keep an eye on the fruits of your labor.
Not just use git but know how git symbolic-ref work
Superheros come in all shapes and sizes.
Fix rejection error in Hexo
The heart can see what is invisible to the eye.
Guide to code productively, get more time back for you
The heart can see what is invisible to the eye.
Is Fibonacci sequence that starts with 0 or 1
The best way to predict the future is to create it.
To increase your productivity 10 times, learn expect and read this blog
Som are born beautiful. The rest of us have to work at it.
Treasure Bowl for SQL, helpful for your daily database jobs
Don’t be greedy. Half of something is better than all nothing.
How to fix most permission issues when using Git
The best way to predict the future is to create it.
One killer page to fix most permission issues when using Git
The best way to predict the future is to create it.
How to check your CPU model and Linux distribution in your AWS VM
Lift is short, enjoy the ride.
2022
Magic-in-Micronaut-JPA
The best way to predict the future is to create it.
谷歌地图里面照片的评论和照片在华为手机里面显示不出来
枝上柳棉吹又少, 天涯何处无芳草. –苏轼
Cannot find symbol class Generated or var
The best way to predict the future is to create it.
GraphQL noteworthy points
Life is like the ocean, it goes up and down.
Scripts bible for MySql
Be the Sun of your solar system.
Minium Workable Mvp Vimrc
”—————————————————————- “ 4. User interface “—————————————————————- “ Set X lines to the cursor when moving vertically set scrolloff=0
How to build unit/integration tests for Spring State Machine
Get busy living or get busy dying.
Magic after maven target spring-boot-run
Turn your wounds into wisdom
Bamboo pipeline deployment failure caused by Kubenetes Finalizer
Today a reader, tomorrow a leader.
Error in WSL in windows, command not found: sdk
Never stop learning, because life never stops teaching.
Could not write JSON: Value out of range. Value: “xxxxx” Radix:10
Life is really simple, but men insist on making it complicated.
Gemfire Geode Error on Peer or client version with ordinal xx not supported. Highest known version is 1.12.1 Client
Take the risk or lose the chance!
Password must not null in gemfire and geode, but I’ve assigned password in yaml properties file
Worries less, smile more!
One page to cover most commonly found errors for fat jar in SpringBoot
Kill time, or kiss time!
Awesome Shortcuts to boost productivity
One must learn by doing the thing; for though you think you know it, you have no certainty, until you try. —Sophocles
Core Java tips required an interview
Success is the sum of small efforts, repeated.
Tell me difference of truststore and keystore in short answer
Do what you say, say what you do.
GIT useful scripts or error solutions
Don’t wish for it, work for it.
Tell me difference of yarn install and npm install in short answer
Don’t find fault. Find a remedy.
Bible blog for most commonly found Gradle errors
People are smarter than you think. Give them a chance to prove themselves.
Pearls in Front end development
Be happy in front of people who don’t like you, it kills them.
Ruby from zero to hero
This is your life. Do what you love, and do it often.
Everything you’d know for Groovy interviews
Life is short. Don’t waste it with negative people who don’t appreciate you. Keep them in your heart but keep them out of your life.
To outstanding as professional MacBook pro user
The most effective way to do it, is to do it Homebrew The best practice is to run brew info before install new software. It will generally list what’s c...
Failed to install gem in Mac, incompatible architecture and missing psych
Burn your ego before it burns you.
IntelliJ Tips to boost your productivity 10 times
Don’t be afraid to make s splash.
Everything you’d know about state machine for interviews
Less expecting, more accepting.
Tips about algorithm resolving from Leetcode
Stay focused, believe that you can achieve at the highest level, surround yourself with others who believe in you and do not stray from your goals.
Solution center for Node errors
Fina a way. If there’s none, make one!
Triple your productivities by Visual studio code keyboard shortcuts
The sentence The quick brown fox jumps over the lazy dog uses every letter of the alphabet.
TypeScript noteworthy notes
The moment you start focusing on yourself, things start falling into place.
RXJS – reactive Programming like a hero
When love is real, it doesn’t lie, cheat, pretend or keep secrets.
Concurrency in Java
Little things make big things happens.
Linux Tips
Remember, some things have to end for better things to begin.
A taste of GraphQL
A good day starts with a good mindset!
A taste of GraphQL
A good day starts with a good mindset!
What’s inside magic in Spring Data JPA
A good day starts with a good mindset!
What’s inside magic in Spring Data JPA
A good day starts with a good mindset!
Why Spring turn a column name from camelNaming to snake_Naming
Don’t spend another year doing the same shit.
Some mistakes you’d avoid in java
With great power comes great responsibilities.
Untold stories for Jupiter, any differences JUnit 5 vs Junit 4
Don’t tell people your plans. Just show them your results!
Git commands you can show off for 100 years
Life is short, make a big splash!
FileNotFound Exception when loading data file in IntelliJ
Take time to do what makes your soul happy!
How to ace AWS certification just like play a game
Life isn’t about finding yourself. Life is about creating yourself.
Java Deep Notes
Java Deep Notes
Code to draw a Big H with all stars
Coding is everything! Code Now!
Code to draw a Big H with all stars
Coding is everything! Code Now!
Single vs Double precisions, float vs double data type
Leave nothing for tomorrow which can be done today. -Abraham Lincoln.
SkipTest-Not-Work-In-Multiple-models-project
Leave nothing for tomorrow which can be done today. -Abraham Lincoln.
SkipTest-Not-Work-In-Multiple-models-project
Leave nothing for tomorrow which can be done today. -Abraham Lincoln.
Maven error and solution on No such host is known
Don’t promis when you are hapy. Don’t reply when you’re angry and don’t decide when you’re sad Service keep on restarting If you spot service is restartin...
Maven error and solution on No such host is known
Don’t promis when you are hapy. Don’t reply when you’re angry and don’t decide when you’re sad
Gradle build stuck
Gradle build stuck, keep on running but never ending
2021
Save my eyes, let your cell phone to read screen content to you
Too much screen time
How logging system Bootstrapped in Spring Boot Application
Summary Following diagram demonstrated the process to bootstrap and use Logback for loggings in Spring Boot applciation.
SQLServer Error about This driver is not configured for integrated authentication
Symptoms When you are using integrated authentication (Kerberos connection) for MS SqlServer connection, there is one possible error :
How to copy files from resources folder in jar and save to a file
Why to extract resources from jar to local disk
Debug of SpringBoot run not working in IntelliJ
Normal approach to debug maven
How to watch specific kubenetes deployment by labels
How to watch specific kubenetes deployment by labels
Failed to talk to github.com from corporation network
Background It’s typical to get various network connection issues when you run commands within corporation network. For example, you’ll find diversed issues w...
Day-Day-Up-Java
More developer friendly Threa Sleep
How to user fire extinguisher
Summary As you know, staff and your safety is paramount. So what if emergency take place, such as fire in office, how to help yourself and your colleagues by...
Deep dive into ApplicationEvent in SpringBoot
Summary As you know, there are various event will be sent (multicast) when a specific story taken place.
2021-09-22-IT-Solutions-For-Remote-Learning
IT-Solutions-For-Remote-Learning.md
Deep dive into Kubernetes Client API
Summary To talk to K8s for getting data, there are few approaches. While K8s’ official Java library is the most widely used one. This blog will look into thi...
How to get CPU name, core, 64bit and speed in command line
Summary In windows operating system, if you want to get your CPU name, core, 64bit and speed in command line. Just follow below actions:
JetBrains/IntelliJ tips
Be a good person in real life, not in social media
Whitelabel Error Page
Summary Whitelabel Error Page is the default error page in Spring Boot web app. It provide a more user-friently error page whenever there are any issues when...
Google maps no photos reviews
Summary
谷歌地图里面照片的评论显示不出来
If you’d like to view solution in YouTube, check out at https://youtu.be/ICiwuqJ-yU8
Shall I still need booster even after I got dose 3?
The greatest wealth is health!
Debts in a nutshell
A debt security represents a debt owed by the issuer to an investor. Here, the investor acts as a lender to the issuer which may be a government, organisatio...
2020
How to process data from S3 download URL
S3 download URL As you know, AWS S3 object can be downloaded/processed by S3 download URL. I’m showing you two examples on how to process S3 Object by NIO f...
Debug Stuck IntelliJ
What happened to a debug job hanging in IntelliJ (IDEAS) IDE? You may find when you try to debug a class in Intellij but it stuck there and never proceed, e....
Awesome Kotlin
Difference with Scala Kotlin takes the best of Java and Scala, the response times are similar as working with Java natively, which is a considerable advantag...
Awesome tips for Chrome
Shortcuts & tips
JVM热身
此文是作者英文原文的翻译文章，英文原文在：http://todzhang.com/posts/2018-06-10-jvm-warm-up/
Awesome tips and shortcuts for Slack
Shortcuts for Slack
Awesome Reactive programming
Key points of Reactive Programming
Awesome Swift for iOS
Frame in Swift
Mock in kotlin
Argument Matching & Answers For example, you have mocked DOC with call(arg: Int): Intfunction. You want to return 1 if argument is greater than 5 and -1 ...
Mock in kotlin
Argument Matching & Answers For example, you have mocked DOC with call(arg: Int): Intfunction. You want to return 1 if argument is greater than 5 and -1 ...
Docker
Dockers Concepts
How to decode path parameters in All REST WebServices calls
How to decode path parameters in All REST WebServices calls
Curl
Linux Curl command
AOP
The concept of join points as matched by pointcut expressions is central to AOP, and Spring uses the AspectJ pointcut expression language by default.
Micrometer notes
As a general rule it should be possible to use the name as a pivot. Dimensions allow a particular named metric to be sliced to drill down and reason about th...
Pigeons in holes principle
# Pigeonhole principle
Awesome solutions for algorithm questions
你就会发现只要涉及递归的问题，都是 树的问题。
A Facial Recognition utility in a dozen of LOC
A Facial Recognition utility in a dozen of python LOC (Lines Of Code)
Awesome SSL certificates and HTTPS
What’s TLS TLS (Transport Layer Security) and its predecessor, SSL (Secure Sockets Layer), are security protocols designed to secure the communication betwee...
JVM warm up by Escape Analysis
Why JVM need warm up I don’t know how and why you get to this blog. But I know the key words in your mind are “warm” for JVM. As the name “warm up” suggested...
Java Concurrent Column 2
This is the second half about Java Concurrent of my blog
Java Concurrent
This blog is about noteworthy pivot points about Java Concurrent Framework Back to Java old days there were wait()/notify() which is error prone, while fr...
Algorithm notes from Leecode – 1
Algorithm Leetcode
2019
Conversations with God
Feelings is the language of the soul. If you want to know what’s true for you about something, look to how your’re feeling about.
Kafka In Spring
Enable Kafka listener annotated endpoints that are created under the covers by a AbstractListenerContainerFactory. To be used on Configuration classes as fol...
Terraform
Why Terraform
Kafka
Kafka
Mifid
FX Spot is not covered by the regulation, as it is not considered to be a financial instrument by ESMA, the European Union (EU) regulator. As FX is considere...
Foreign Exchange
currency pairs Direct ccy: means USD is part of currency pair Cross ccy: means ccy wihtout USD, so except NDF, the deal will be split to legs, both with...
2018
Seconds
nano seconds
Citrix receiver
Simple Binary Encoding (SBE)
Citrix receiver
“Cannot connect to remote desktop” with Citrix Receiver
Guice
A new type of Juice Put simply, Guice alleviates the need for factories and the use of new in your Java code. Think of Guice’s @Inject as the new new. You wi...
YAML
Key points All YAML files (regardless of their association with Ansible or not) can optionally begin with — and end with …. This is part of the YAML format a...
Distruptor
multithreading
Mockito
Feature
Protobuf
What are protocol buffers?
Sudo in a Nutshell
Sudo in a Nutshell Sudo (su “do”) allows a system administrator to give certain users (or groups of users) the ability to run some (or all) commands as root...
Zoo-keeper
ZK Motto the motto “ZooKeeper: Because Coordinating Distributed Systems is a Zoo.”
Presto DB
WHAT IS PRESTO?
Chronicle
Overview
Cucumber
Acceptance testing vs unit test It’s sometimes said that unit tests ensure you build the thing right, whereas acceptance tests ensure you build the right thi...
Scala
Scala String
akka framework of scala
philosophy The actor model adopts the philosophy that everything is an actor. This is similar to the everything is an object philosophy used by some object-o...
File Util in Apache Camel
FileUtil.class
Apache Camel
Camel’s message model In Camel, there are two abstractions for modeling messages, both of which we’ll cover in this section. org.apache.camel.Message—The ...
QuickFixJ
Settings
JXM
Exporting your beans to JMX The core class in Spring’s JMX framework is the MBeanExporter. This class is responsible for taking your Spring beans and registe...
Solace MQ
Solace PubSub+ It is a message broker that lets you establish event-driven interactions between applications and microservices across hybrid cloud environmen...
Apigee
App deployment, configuration management and orchestration - all from one system. Ansible is powerful IT automation that you can learn quickly.
Ansible
Ansible: What Is It Good For? Ansible is often described as a configuration management tool, and is typically mentioned in the same breath as Chef, Puppet, a...
flexbox
How Flexbox works — explained with big, colorful, animated gifs
Jboss tips
commands:
Locking and multithreading
Single Writer principle
KDB
KDB However kdb+ evaluates expressions right-to-left. There are no precedence rules. The reason commonly given for this behaviour is that it is a much simple...
Foreign Exchange
Foreign Exchange markets
Portactor
Better to use smart wait
Agile and SCRUM
Key concept In Scrum, a team is cross functional, meaning everyone is needed to take a feature from idea to implementation.
DevOps-Philosophy
:100:DevOps Model Defined
rxjs pipe in depth
https://stormforger.com/blog/2016/07/08/types-of-performance-testing/
How to setup nodejs to install package from intranet
Error of ‘ECONNRESET’ You may face error ECONNRESET from intranet, even appropriate proxy tools (e.g. cntlm) is running. The errors may looks like ```bash $ ...
Strategy-Of-Openshift-Releases
Release & Testing Strategy There are various methods for safely releasing changes to Production. Each team must select what is appropriate for their own ...
NodeJs Notes
commands to read files var lineReader = require(‘readline’).createInterface({ input: require(‘fs’).createReadStream(‘C:\dev\node\input\git_reset_files.tx...
Minium Viable Product
https://blog.leanstack.com/minimum-viable-product-mvp-7e280b0b9418
What is difference between declarations, providers and import in NgModule
What is difference between declarations, providers and import in NgModule
CORS :Cross-Origin Resource Sharing
Cross-Origin Request Sharing - CORS (A.K.A. Cross-Domain AJAX request) is an issue that most web developers might encounter, according to Same-Origin-Policy,...
ngrx
Why @Effects? In a simple ngrx/store project without ngrx/effects there is really no good place to put your async calls. Suppose a user clicks on a button or...
iOS programming
View A view is also a responder (UIView is a subclass of UIResponder). This means that a view is subject to user interactions, such as taps and swipes. Thus,...
2017
cloud computering
openshift vs openstack The shoft and direct answer is `OpenShift Origin can run on top of OpenStack. They are complementary projects that work well together....
cloud computering
Concepts Cloud computing is the on-demand demand delivery of compute database storage applications and other IT resources through a cloud services platform v...
Redux
whats @Effects You can almost think of your Effects as special kinds of reducer functions that are meant to be a place for you to put your async calls in suc...
reactive programing
The second advantage to a lazy subscription is that the observable doesn’t hold onto data by default. In the previous example, each event generated by the in...
common errors in NPM or node
code E503 code E503 when run npm install packages, e.g.
Container
The Docker project was responsible for popularizing container development in Linux systems. The original project defined a command and service (both named do...
promise vs observiable
The drawback of using Promises is that they’re unable to handle data sources that produce more than one value, like mouse movements or sequences of bytes in ...
Openshift tips
Commands bible
google analysis
How Page Value is calculated
JDK source
interface RandomAccess Marker interface used by List implementations to indicate that they support fast (generally constant time) random access. The primary ...
SSH SFTP
Secure FTP SFTP over FTP is the equivalant of HTTPS over HTTP, the security version
Setup WebSphere profiles and application in command line
Setup WebSphere profiles and application in command line
AWS Tips
After establishing a SSH session, you can install a default web server by executing sudo yum install httpd -y. To start the web server, type sudo service htt...
Oracle
ORA-12899: Value Too Large for Column
Spring notes
Spring Bean Life Cycle Callback Methods
Kindle notes
#《亿级流量网站架构核心技术》目录一览 TCP四层负载均衡 使用Hystrix实现隔离 基于Servlet3实现请求隔离 限流算法 令牌桶算法 漏桶算法 分布式限流 redis+lua实现 Nginx+Lua实现 使用sharding-jdbc分库分表 Disruptor+Redis...
Java JIT compiler
This is talking about Java JIT (Just-In-Time) compiler
Java Security Notes
Java Security well-behaved: programs should be prevent from consuming too much system resources
SeriableVersionUID
Noteworthy points about SeriableVersionUID in Java
R Language
s<-read.csv("C:/Users/xxx/dev/R/IRS/SHH_SCHISHG.csv") # aggregate s2<-table(s$Original.CP) s3<-as.data.frame(s2) # extract by Frequency ordered s3...
SSH and Cryptography
SFTP versus FTPS SS: Secure Shell An increasing number of our customers are looking to move away from standard FTP for transferring data, so we are ofte...
Eclipse notes
How do I remove a plug-in? Run Help > About Eclipse > Installation Details, select the software you no longer want and click Uninstall. (On Macintosh i...
Java JVM
Class loading subsystem
Maven-Notes
Maven philosophy “It is important to note that in the pom.xml file you specify the what and not the how. The pom.xml file can also serve as a documentatio...
Java New IO
Notes JDK 1.0 introduced rudimentary I/O facilities for accessing the file system (to create a directory, remove a file, or perform another task), accessi...
Network Protocols
Net Protocols
IT-Architect
SOA SOA is a set of design principles for building a suite of interoperable, flexible and reusable services based architecture. top-down and bottom-up a...
Algorithm
This page is about key points about Algorithm
Dead Lock
Concept
Java-Tricky-Tech-Questions.md
What is the difference between Serializable and Externalizable in Java? In earlier version of Java, reflection was very slow, and so serializaing large ob...
NavigableMap Misc
What is NavigableMap
Compare-In-Java
Concepts If you implement Comparable interface and override compareTo() method it must be consistent with equals() method i.e. for equal object by equals(...
Java Collections Misc
Difference between equals and deepEquals of Arrays in Java Arrays.equals() method does not compare recursively if an array contains another array on oth...
HashMap in JDK
Hashmap in JDK Some note worth points about hashmap Lookup process Step# 1: Quickly determine the bucket number in which this element may resid...
Java 8 Tips
This blog is listing key new features introduced in Java 8
Arbitrage vs Heading
What is the difference between arbitrage and hedging?
Java Enum Misc
Enum Misc
2016
Java GC notes
verbose:gc verbose:gc prints right after each gc collection and prints details about each generation memory details. Here is blog on how to read verbose gc
Hash Code Misc
contract of hashCode : Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consis...
Apache Tips
Apache
Angulary Misc
Dependency Injection Angular doesn’t automatically know how you want to create instances of your services or the injector to create your service. You must co...
Random number in java
ThreadLocalRandom, SecureRandm, java.util.Random, java.math.Random
Java new features
JDK Versions JDK 1.5 in 2005 JDK 1.6 in 2006 JDK 1.7 in 2011 JDK 1.8 in 2014 Sun之前风光无限，但是在2010年1月27号被Oracle收购。 在被Oracle收购后对外承诺要回到每2年一个realse的节奏。但是20...
用10几行代码自己写个人脸识别程序
用10几行代码自己写个人脸识别程序
Eslastic Search
Eslastic Search
JSON lines
JSON lines
Python Scraphy
Python Scraphy
Simpler chronicle of CI(Continuous Integration) “乱弹系列”之持续集成工具
引言 有句话说有人的地方就有江湖，同样，有江湖的地方就有恩怨。在软件行业历史长河（虽然相对于其他行业来说，软件行业的历史实在太短了，但是确是充满了智慧的碰撞也是十分的精彩）中有一些恩怨情愁，分分合合的小故事，比如类似的有，从一套代码发展出来后面由于合同到期就分道扬镳，然后各自发展成独门产品的Sybase DB和微...
Head First Blockchina 3
Hyperledger Fabric for Mortals
【原创】深入浅出区块链系统：第二章
使用Solidity创建以太坊(Ethereum)智能合约(Smart Contract)
How to customize Sublime syntax highlights
Reference Sublime Scope Naming Syntax Guide
浅谈软件单元测试中的“断言” (assert)，从石器时代进步到黄金时代。
大家都知道，在软件测试特别是在单元测试时,必用的一个功能就是“断言”（Assert)，可能有些人觉得不就一个Assert语句，没啥花头，也有很多人用起来也是懵懵懂懂，认为只要是Assert开头的方法，拿过来就用。一个偶然的机会跟人聊到此功能，觉得还是有必要在此整理一下如何使用以及对“断言”的理解。希望可以帮助大家...
Head First Blockchina 1
深入浅出区块链系统：第一章. what you should know about blockchain
Kubernetes 与 Docker Swarm的对比
Kubernetes 和Docker Swarm 可能是使用最广泛的工具，用于在集群环境中部署容器。但是这两个工具还是有很大的差别。
漫谈开发设计中的一些‘原则’及’设计哲学’
在开发设计中有一些常用原则或者潜规则，根据笔者的经验，这里稍微总结一下最最常用的，以飨读者。
http methods
RFC origion http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.1.2)
Spark-vs-Storm
The stark difference among Spark and Storm. Although both are claimed to process the streaming data in real time. But Spark processes it as micro-batches; wh...
微服务
可以想像一下，之前的传统应用系统，像是一个大办公室里面，有各个部门，销售部，采购部，财务部。办一件事情效率比较高。但是也有一些弊端，首先，各部门都在一个房间里。
unmodifiableList, unmodifiableSet,unmodifiableMap
What’s it Returns an unmodifiable view of the specified set. This method allows modules to provide users with “read-only” access to internal sets. Query ope...
kibana, view layer of elasticsearch
What’s Kibana kibana is an open source data visualization plugin for Elasticsearch. It provides visualization capabilities on top of the content indexed on...
kibana, view layer of elasticsearch
What’s Kibana kibana is an open source data visualization plugin for Elasticsearch. It provides visualization capabilities on top of the content indexed on...
Anatomy of ThreadLocal
Design philosophies
iConnect
UI HTML5, AngularJS, BootStrap, REST API, JSON Backend Hadoop core (HDFS), Hive, HBase, MapReduce, Oozie, Pig, Solr
Business Analysis
Purpose of BA 带来一些商业价值（收益） 解决业务痛点
Something about RESTful architect
REST API must be hypertext driver Roy’s interview
Data Structure
Binary Tree A binary tree is a tree in which no node can have more than two children. A property of a binary tree that is sometimes important is that th...
Useful bookmarks
eBooks list of various books Node.js
heavy load web application
Common solutions
tips in as400 IBM Emulator
Toggle crosshair
Mysql operator to extract JSON
“Be the change you wish to see in the world.” - Mahatma Gandhi
equity trading
Difference between mutal funds and hedge funds
SQL
Differences between not in, not exists , and left join with null
HTTPS/2
concepts
Github page commands notes
404 error for customized domain (such as godday) 404 There is not a GitHub Pages site here. Go to github master branch for gitpages site, manually add CN...
RenMinBi International
RQFII RQFII stands for Renminbi Qualified Foreign Institutional Investor. RQFII was introduced in 2011 to allow qualified foreign institutional investors to ...
JavaScript tips
includes() vs some()
Docker Errors and Fixes
Docker Errors
Load Balancing
Concepts LVS means Linux Virtual Server, which is one Linux built-in component.
Python
(‘—–Unexpected error:’, <type ‘exceptions.TypeError’>) datetime.datetime.now()
Storage Management
RAID RAID is Reductant Array Independent Disk,
CI and CD
Concepts
XA Transactions in 2PC
Description
Setup Git in Mint Linux
How to setup Git in Mint Linux =================================================
Database sharding
DB sharding in YHD
Microservices vs. SOA
Microservice Services are organized around capabilities, e.g., user interface front-end, recommendation, logistics, billing, etc. Services are small in ...
Java Class Loader
Codecache The maximum size of the code cache is set via the -XX:ReservedCodeCacheSize=N flag (where N is the default just mentioned for the particular com...