There are over 40 functional interfaces listed in the java.util.functions package, which can make the prospect of functional programming in Java ... This restriction doesn’t apply to the Function ...

java.util.function.UnaryOperator @FunctionalInterface public interface UnaryOperator<T> extends Function<T,T> T apply(T t) Applies this function to the given argument. Parameter Types: T - the input ...

In addition to writing for JavaWorld, he has written his own Java book for beginners— Java 2 by Example, Second Edition (Que Publishing, 2001; ISBN: 0789725932)—and helped write Using Java 2 ...