位运算实现多状态控制

　　经常在源码阅读过程中，遇到一个状态标志位去标识多个状态，并对多状态进行控制的操作，下面是对多状态控制的一个总结:

public class Main {
    public static final int SET_MOBILE = 0x1;
    public static final int SET_SMS_CODE = 0x2;
    public static final int SET_PASSWORD = 0x3;
    public static final int REGISTER = 0x4;

    public static Boolean isExistState(int currentSate, int targetSate) {
        return (currentSate & targetSate) == targetSate;
    }

    public static int cancelState(int currentSate, int targetSate) {
        return currentSate & ~targetSate;
    }

    public static void main(String[] args) {
        // 设置mRegisterState 目前有3个状态
        int mRegisterState = SET_MOBILE | SET_SMS_CODE | SET_PASSWORD;
        System.out.println("===========初始化状态，包含 SET_MOBILE  SET_SMS_CODE  SET_PASSWORD======================");
        System.out.println("存在状态SET_SMS_CODE : "+isExistState(mRegisterState, SET_SMS_CODE));
        System.out.println("存在状态REGISTER : "+isExistState(mRegisterState, REGISTER));
        System.out.println("存在状态SET_PASSWORD : "+isExistState(mRegisterState, SET_PASSWORD));

        System.out.println("=====================去除状态SET_SMS_CODE===========================");
        mRegisterState = cancelState(mRegisterState, SET_SMS_CODE);
        System.out.println("存在状态SET_SMS_CODE : "+isExistState(mRegisterState, SET_SMS_CODE));
        System.out.println("===========================去除状态SET_PASSWORD======================");
        mRegisterState &= ~SET_PASSWORD;
        System.out.println("存在状态SET_PASSWORD : "+isExistState(mRegisterState, SET_PASSWORD));

        System.out.println("===================添加状态REGISTER==================");
        mRegisterState |= REGISTER;
        System.out.println("存在状态REGISTER : "+isExistState(mRegisterState, REGISTER));

        System.out.println("===================“反转”操作：如果SET_SMS_CODE在组中，则从组中删除之；否则将SET_SMS_CODE加入组中==================");
        mRegisterState ^= SET_SMS_CODE;
        System.out.println("存在状态SET_SMS_CODE : "+isExistState(mRegisterState, SET_SMS_CODE));

        System.out.println("==================清空所有状态=======================");
        mRegisterState = 0;
        System.out.println("存在状态SET_SMS_CODE : "+isExistState(mRegisterState, SET_SMS_CODE));
        System.out.println("存在状态REGISTER : "+isExistState(mRegisterState, REGISTER));
        System.out.println("存在状态SET_PASSWORD : "+isExistState(mRegisterState, SET_PASSWORD));
        System.out.println("存在状态REGISTER : "+isExistState(mRegisterState, REGISTER));

        System.out.println("==================添加所有状态=======================");
        mRegisterState = ~0;
        System.out.println("存在状态SET_SMS_CODE : "+isExistState(mRegisterState, SET_SMS_CODE));
        System.out.println("存在状态REGISTER : "+isExistState(mRegisterState, REGISTER));
        System.out.println("存在状态SET_PASSWORD : "+isExistState(mRegisterState, SET_PASSWORD));
        System.out.println("存在状态REGISTER : "+isExistState(mRegisterState, REGISTER));
    }
}