Review the Comparator class; it has two abstract methods, why it can be a function interface? Comparator.java package java.util; @FunctionalInterface public interface Comparator<T> { // abstract method int compare(T o1, T o2); // abstract method boolean equals(Object obj); // few default and static methods } Definition of function interface Conceptually, a functional interface has exactly …
In Java 8, BinaryOperator is a functional interface and it extends BiFunction. The BinaryOperator takes two arguments of the same type and returns a result of the same type of its arguments. BinaryOperator.java @FunctionalInterface public interface BinaryOperator<T> extends BiFunction<T,T,T> { } The BiFunction takes two arguments of any type, and returns a result of any …
In this example, we will show you how to use Java 8 Lambda expression to write a Comparator to sort a List. 1. Classic Comparator example. Comparator<Developer> byName = new Comparator<Developer>() { @Override public int compare(Developer o1, Developer o2) { return o1.getName().compareTo(o2.getName()); } }; 2. Lambda expression equivalent. Comparator<Developer> byName = (Developer o1, Developer o2)->o1.getName().compareTo(o2.getName()); …