冒号（:)运算符做什么？

在Java代码中冒号有几个地方：

1）跳出标签）：

label: for (int i = 0; i < x; i++) {    for (int j = 0; j < i; j++) {        if (something(i, j)) break label; // jumps out of the i loop    }} // i.e. jumps to here

2）三元条件：

int a = (b < 4)? 7: 8; // if b < 4, set a to 7, else set a to 8

3）每个循环：

String[] ss = {"hi", "there"}for (String s: ss) {    print(s); // output "hi" , and "there" on the next iteration}

4）断言：

int a = factorial(b);assert a >= 0: "factorial may not be less than 0"; // throws an AssertionError with the message if the condition evaluates to false

5）切换语句中的情况：

switch (type) {    case WHITESPACE:    case RETURN:        break;    case NUMBER:        print("got number: " + value);        break;    default:        print("syntax error");}

6）方法参考

class Person {   public static int compareByAge(Person a, Person b) {       return a.birthday.compareTo(b.birthday);   }}}Arrays.sort(persons, Person::compareByAge);