BinaryOperator 二元操作符， 传入的两个参数的类型和返回类型相同， 继承BiFunction
BinaryOperator<T>：两个T作为输入，返回一个T作为输出，对于“reduce”操作很有用
BinaryOperator<String> bina = (x, y) -> x + " " + y;
BinaryOperator<Integer> reduce = (x, y) -> x - y;
BinaryOperator<Double> div = (x, y) -> {
if (y == 0){
System.out.println("除数不能为0");
}
return x / y;
} ;
System.out.println(bina.apply("hello ", "world")); // hello world
System.out.println(reduce.apply(10, 2)); // 8
System.out.println(div.apply(10.2, 0.0)); // Infinity
源码查看
@FunctionalInterface
public interface BinaryOperator<T> extends BiFunction<T,T,T> {
/**
* Returns a {@link BinaryOperator} which returns the lesser of two elements
* according to the specified {@code Comparator}.
*
* @param <T> the type of the input arguments of the comparator
* @param comparator a {@code Comparator} for comparing the two values
* @return a {@code BinaryOperator} which returns the lesser of its operands,
* according to the supplied {@code Comparator}
* @throws NullPointerException if the argument is null
*/
public static <T> BinaryOperator<T> minBy(Comparator<? super T> comparator) {
Objects.requireNonNull(comparator);
return (a, b) -> comparator.compare(a, b) <= 0 ? a : b;
}
/**
* Returns a {@link BinaryOperator} which returns the greater of two elements
* according to the specified {@code Comparator}.
*
* @param <T> the type of the input arguments of the comparator
* @param comparator a {@code Comparator} for comparing the two values
* @return a {@code BinaryOperator} which returns the greater of its operands,
* according to the supplied {@code Comparator}
* @throws NullPointerException if the argument is null
*/
public static <T> BinaryOperator<T> maxBy(Comparator<? super T> comparator) {
Objects.requireNonNull(comparator);
return (a, b) -> comparator.compare(a, b) >= 0 ? a : b;
}
}
