坑【1】Switch

public class SwitchTest {    public static void main(String[] args) {        doSex(new String());//正常执行         doSex(null);//空指针 switch不能跟Null    }    public static void doSex(String sex) {        switch (sex) {        case "d":            System.out.println("男的");            break;        case "dd":            System.out.println("女的");            break;        default:            System.out.println("出错");            break;        }    }}