Java8 常用FunctionInterface使用方法

package com.lgx.jdk8.part02;import java.util.*;import java.util.function.*;/** * java.util.function包API自学 */public class Test06LearnBySelf {    public static void main(String[] args) {        /**Consumer:接收一个参数不返回值，functional method is accept(Object)**/        List<String> list = Arrays.asList("hello", "world");        list.forEach(new Consumer<String>() {            @Override            public void accept(String s) {                System.out.println("s = " + s.toUpperCase());            }        });        list.forEach(item -> System.out.println(item.toUpperCase()));        /**DoubleConsumer:接收一个Double参数不返回值，functional method is accept(double)**/        DoubleConsumer dc = (x) -> System.out.println(x*x);        dc.accept(3.1415);        List<Double> list2 = Arrays.asList(1.11, 2.22);        /*list2.forEach(new DoubleConsumer(){            @Override            public void accept(double value) {            }        });*/ //一直报错？？？原因，forEach方法接受的参数就是Consumer，DoubleConsumer不是Consumer的子类        list2.forEach(item -> System.out.println(item));        /**BiConsumer:接收两个参数不返回值，functional method is accept(Object, Object)**/        Map<String, String> map = new HashMap<>();        map.put("key1", "value1");        map.put("key2", "value2");        map.forEach(new BiConsumer<String, String>() {            @Override            public void accept(String s1, String s2) {                System.out.println("key = " + s1 + ", value = " + s2);            }        });        map.forEach((s1, s2) -> System.out.println("key = " + s1 + ", value = " + s2));        System.out.println("================================================================");        /**Function:接收一个参数返回一个值，functional method is apply(Object)**/        Function<String, String> function = (s1) -> s1.toUpperCase();        String result = function.apply("hello world");        System.out.println("result = " + result);        /**IntFunction:接收一个Int参数返回一个Int值，functional method is apply(int)**/        IntFunction<Integer> intFunction = (int1) -> int1 * int1;        int intResult = intFunction.apply(100);        System.out.println("intResult = " + intResult);        /**DoubleToIntFunction:接收一个double参数返回一个int值，functional method is applyAsInt(Object)**/        DoubleToIntFunction doubleToIntFunction = (d1) -> (int)d1+2;        int doubleToIntResult = doubleToIntFunction.applyAsInt(3.1415926);        System.out.println("doubleToIntResult = " + doubleToIntResult);        /**BiFunction:接收两个参数返回一个值，functional method is apply(Object, Object)**/        BiFunction<String, String, String> biFunction = (s1, s2) -> s1 + s2;        String biResult = biFunction.apply("hello", "world");        System.out.println("biResult = " + biResult);        /**BinaryOperator(二元运算符):接收两个参数返回一个值（参数和返回值类型是一致的），functional method is apply(Object, Object)**/        BinaryOperator<Double> binaryOperator = (d1, d2) -> d1 + d2;        double binaryResult = binaryOperator.apply(20.0, 30.0);        System.out.println("binaryResult = " + binaryResult);        double minResult = BinaryOperator.minBy(Double::compareTo).apply(20.0 , 30.0);        System.out.println("minResult = " + minResult);        double maxResult = BinaryOperator.maxBy(Double::compareTo).apply(20.0 , 30.0);        System.out.println("maxResult = " + maxResult);        System.out.println("================================================================");        /**Predicate:接收一个参数返回一个boolean值，functional method is test(Object)**/        Predicate<String> predicate = (a) -> a == null;        boolean predicateResult = predicate.test(new String());        System.out.println("predicateResult = " + predicateResult);        /**DoublePredicate:接收一个参数返回一个boolean值，functional method is test(double)**/        DoublePredicate doublePredicate = (d) -> d >= 10;        boolean doublePredicateResult = doublePredicate.test(9.99999);        System.out.println("doublePredicateResult = " + doublePredicateResult);        /**BiPredicate:接收两个参数返回一个boolean值，functional method is test(Object, Object)**/        BiPredicate<Integer, Integer> biPredicate = (b1, b2) -> b1 > b2;        boolean biPredicateResult = biPredicate.test(3, 2);        System.out.println("biPredicateResult = " + biPredicateResult);        System.out.println("================================================================");        /**Supplier:不接受参数返回一个值，functional method is get(Object)**/        Supplier<String> supplier = () -> "test";        String supplierResult = supplier.get();        System.out.println("supplierResult = " + supplierResult);        /**DoubleSupplier:不接受参数返回一个Double值，functional method is getAsDouble()**/        DoubleSupplier doubleSupplier = () -> 1;        double doubleSupplierResult = doubleSupplier.getAsDouble();        System.out.println("doubleSupplierResult = " + doubleSupplierResult);        System.out.println("================================================================");    }}