Java: use Objects#requireNonNull() for argument validation

[yamgent]

A typical check for null in argument would be as follow:

void doSomething(Bar bar) {
    if (bar == null) {
        throw new NullPointerException();
    }
    bar.doMoreThings();
    ...
}

We can use Java's Objects#requireNonNull(T) helper method instead. It automatically throws a NullPointerException for us.

void doSomething(Bar bar) {
    requireNonNull(bar);
    bar.doMoreThings();
    ...
}

For setters and constructors, we can also "inline" this check, by doing this:

public Foo(Bar bar) {
    this.bar = Objects.requireNonNull(bar);
}

Note that this is only allowed if it is a direct assignment, otherwise, never inline it.

[yamgent]

Google's Guava library also has more helper methods for different kinds of argument validation, although that means we will have a new dependency, so projects should probably write their own version of the helper methods:

https://github.com/google/guava/wiki/PreconditionsExplained