java8::(JDK8双冒号)具有什么功能呢？

jdk8中双冒号的功能:
     将方法作为参数传入至stream内部
	 stream内部中每个元素都会放入到方法中运行

public class TestClass {
    public static void  printValur(String str){
        System.out.println("print value : "+str);
    }

    public static void main(String[] args) {
        list<String> al = Arrays.asList("a","b","c","d");
        for (String a: al) {
            TestClass.printValur(a);
        }

        al.forEach(x->{
            TestClass.printValur(x);
        });
    }
}

public class MyTest {
    public static void  printValur(String str){
        System.out.println("print value : "+str);
    }

    public static void main(String[] args) {
        List<String> al = Arrays.asList("a", "b", "c", "d");
        al.forEach(TestClass::printValur);

        //下面的方法和上面等价的
        Consumer<String> methodParam = TestClass::printValur; //方法参数
        al.forEach(x -> methodParam.accept(x));//方法执行accept
    }
}