JDK8新特性-java.util.function-Function接口使用

//将Function对象应用到输入的参数上，然后返回计算结果。
R apply(T t);

//返回一个先执行当前函数对象apply方法再执行after函数对象apply方法的函数对象。
default <V> Function<T, V> andThen(Function<? super R, ? extends V> after) {
        Objects.requireNonNull(after);
        return (T t) -> after.apply(apply(t));
    }

//返回一个先执行before函数对象apply方法再执行当前函数对象apply方法的函数对象
default <V> Function<V, R> compose(Function<? super V, ? extends T> before) {
        Objects.requireNonNull(before);
        return (V v) -> apply(before.apply(v));
    }

public static void main(String[] args) {
        Function<Integer, Integer> name = e -> e * 2;
        Function<Integer, Integer> square = e -> e * e;
        int value = name.andThen(square).apply(3);
        System.out.println("andThen value=" + value);
        int value2 = name.compose(square).apply(3);
        System.out.println("compose value2=" + value2);
        //返回一个执行了apply()方法之后只会返回输入参数的函数对象
        Object identity = Function.identity().apply("huohuo");
        System.out.println(identity);
    }

public class MyFunction implements Function<String,Integer>{

    @Override
    public Integer apply(String s) {
        return s.length();
    }
}

public class MyBiFunction implements BiFunction<String, String, String> {
    @Override
    public String apply(String s, String s2) {
        return s+";"+s2;
    }
}

private static String hello = "Nice to meet you";
    private static String name = "my name is huohuo";

    public static void main(String[] args) {
        MyFunction myFunction = new MyFunction();
        MyBiFunction biFunction = new MyBiFunction();
        int num = myFunction.apply(hello);
        String valueBi = biFunction.apply(hello, name);
        //hello长度返回
        System.out.println(num);
        //语句整合返回
        System.out.println(valueBi);
    }