Java Deep Notes

Java Deep Notes

How to avoid NPE null in middle of Java Lambda

The key is add a step .filter(Objects::nonNull) Here is a usage sample:

dataMap.keySet().stream()
                .map(discountMapping::get)
                .filter(Objects::nonNull)
                .map(it -> it.applyDiscount(this))
                .reduce(BigDecimal.ZERO, BigDecimal::add);

Is string concatenation a devil?

In fact, a string concatenation is going to be just fine, as the javac compiler will optimize the string concatenation as a series of append operations on a StringBuilder anyway. Here’s a part of the disassembly of the bytecode from the for loop from the above program: