JDK8_方法引用

//方法引用
public class LambdaTest2 {

    @Test
    public void test(){
        Consumer<String> consumer = new Consumer<String>() {
            @Override
            public void accept(String s) {
                System.out.println("I lived in "+s+" for last year");
            }
        };
        consumer.accept("China");

        //lambda
        Consumer<String> consumer1 = s -> System.out.println("I lived in "+s+" for last year");
        consumer1.accept("USA");

        //方法引用 情况一: 对象 :: 实例方法
        PrintStream ps = System.out;
        Consumer<String> consumer2 =ps::println;
        consumer2.accept("Germany");

    }

    @Test
    public void test2(){
        Function<Double,Long> function = new Function<Double, Long>() {
            @Override
            public Long apply(Double aDouble) {
                return Math.round(aDouble);
            }
        };
        System.out.println(function.apply(12.5));

        //lambda
        Function<Double,Long> function1 = (aDouble) -> Math.round(aDouble);
        System.out.println(function.apply(13.5));

        //方法引用 情况二:  类 :: 静态方法
        Function<Double,Long> function2 =Math::round;
        System.out.println(function.apply(14.5));
    }

    @Test
    public void test3(){
        //原来的写法
        Comparator<Integer> comparator = new Comparator<Integer>() {
            @Override
            public int compare(Integer o1, Integer o2) {
                return o1.compareTo(o2);
            }
        };
        System.out.println(comparator.compare(12,32));

        //lambda
        Comparator<Integer> comparator1 = (t1,t2) ->t1.compareTo(t2);
        System.out.println(comparator1.compare(65,34));

        //方法引用 情况三:  类 :: 实例方法
        //Comparator<Integer> comparator2 =Integer::compareTo;
        Comparator<Integer> comparator2 =Integer::compare;
        System.out.println(comparator2.compare(55,65));
    }


}