Java 位运算符

Java 位运算符

位运算符

Java定义了位运算符，应用于整数类型(int)，长整型(long)，短整型(short)，字符型(char)，和字节型(byte)等类型。

位运算符作用在所有的位上，并且按位运算。假设a = 60，b = 13;它们的二进制格式表示将如下：

A = 0011 1100
B = 0000 1101
-----------------
A&B = 0000 1100
A | B = 0011 1101
A ^ B = 0011 0001
~A= 1100 0011

下表列出了位运算符的基本运算，假设整数变量 A 的值为 60 和变量 B 的值为 13：

操作符	描述	例子
&	如果相对应位都是1，则结果为1，否则为0	（A＆B），得到12，即0000 1100
|	如果相对应位都是 0，则结果为 0，否则为 1	（A | B）得到61，即 0011 1101
^	如果相对应位值相同，则结果为0，否则为1	（A ^ B）得到49，即 0011 0001
〜	按位取反运算符翻转操作数的每一位，即0变成1，1变成0。	（〜A）得到-61，即1100 0011
<<	按位左移运算符。左操作数按位左移右操作数指定的位数。	A << 2得到240，即 1111 0000
>>	按位右移运算符。左操作数按位右移右操作数指定的位数。	A >> 2得到15即 1111
>>>	按位右移补零操作符。左操作数的值按右操作数指定的位数右移，移动得到的空位以零填充。	A>>>2得到15即0000 1111

实例

下面的简单示例程序演示了位运算符。复制并粘贴下面的Java程序并保存为Test.java文件，然后编译并运行这个程序：

public class Test { 
    public static void main(String[] args) {
        int a = 60; / 60 = 0011 1100 /
        int b = 13; / 13 = 0000 1101 /
        int c = 0;
        c = a & b;       / 12 = 0000 1100 / 
        System.out.println("a & b = " + c ); 
        c = a | b;       /* 61 = 0011 1101 */
        System.out.println("a | b = " + c );

         c = a ^ b;       /* 49 = 0011 0001 */ 
        System.out.println("a ^ b = " + c );

         c = ~a;          /*-61 = 1100 0011 */ 
        System.out.println("~a = " + c );

         c = a << 2;     /* 240 = 1111 0000 */ 
        System.out.println("a << 2 = " + c );

         c = a >> 2;     /* 15 = 1111 */ 
        System.out.println("a >> 2  = " + c );

         c = a >>> 2;     /* 15 = 0000 1111 */ 
        System.out.println("a >>> 2 = " + c );
                                                           
 }
}

以上实例编译运行结果如下：

a & b = 12
a | b = 61
a ^ b = 49
~a = -61
a << 2 = 240
a >> 2  = 15
a >>> 2 = 15

例子：

位运算记录多选状态

public class TestMain {

    static final int TOP = 1;
    static final int BOTTOM = 1 << 1;
    static final int LEFT = 1 << 2;
    static final int RIGHT = 1 << 3;

    public static void main(String[] args) {
        int[] arr = {TOP, BOTTOM, LEFT, RIGHT, LEFT | TOP, LEFT | BOTTOM, RIGHT | TOP, RIGHT | BOTTOM};

        for (int i : arr) {
            switch (i) {
                case TOP:
                    print("顶部", TOP);
                    break;
                case BOTTOM:
                    print("底部", BOTTOM);
                    break;
                case LEFT:
                    print("左边", LEFT);
                    break;
                case RIGHT:
                    print("右边", RIGHT);
                    break;
                case LEFT | TOP:
                    print("左上角", (LEFT | TOP));
                    break;
                case LEFT | BOTTOM:
                    print("左下角", (LEFT | BOTTOM));
                    break;
                case RIGHT | TOP:
                    print("右上角", (RIGHT | TOP));
                    break;
                case RIGHT | BOTTOM:
                    print("右下角", (RIGHT | BOTTOM));
                    break;
            }
        }
    }

    public static void print(String string, int value) {
        System.out.println(string + ": " + Integer.toBinaryString(value));
    }
}
------------

顶部: 1
底部: 10
左边: 100
右边: 1000
左上角: 101
左下角: 110
右上角: 1001
右下角: 1010

通过位运算实现多个状态的判断

public interface LogConstants {
    /**
     * 消耗标记
     */
    short COST_ASSET = 1 << 0;
    short COST_GOLD = 1 << 1;
    short COST_BINDGOLD = 1 << 2;
    short COST_SOPH = 1 << 3;
    short COST_STRSOUL = 1 << 4;
    short COST_REFSOUL = 1 << 5;
    short COST_SOULSTONE = 1 << 6;
    short COST_AAMHID = 1 << 7;
    short COST_REALM = 1 << 8;
}

short mark = 0;
        int costSoph = channel.getSoph();
        if (costSoph > 0) {
            mark |= LogConstants.COST_SOPH;
        }

        if (costGold > 0) {
            mark |= LogConstants.COST_GOLD;
        }

通过 (m & LogConstants.COST_ASSET) > 0 判断是否拥有该状态

通过 m = (short) (m & ~LogConstants.COST_ASSET);扣除该状态

public void addCostLog(LogEvent event, Player player, short mark, int... args) {short m = mark;
        for (int i : args) {
            if ((m & LogConstants.COST_ASSET) > 0) {
                m = (short) (m & ~LogConstants.COST_ASSET);
                cost.setAsset(i);
            } else if ((m & LogConstants.COST_GOLD) > 0) {
                m = (short) (m & ~LogConstants.COST_GOLD);
                cost.setGold(i);
            } else if ((m & LogConstants.COST_BINDGOLD) > 0) {
                m = (short) (m & ~LogConstants.COST_BINDGOLD);
                cost.setBindGold(i);
            } else if ((m & LogConstants.COST_SOPH) > 0) {
                m = (short) (m & ~LogConstants.COST_SOPH);
                cost.setSoph(i);
            } else if ((m & LogConstants.COST_STRSOUL) > 0) {
                m = (short) (m & ~LogConstants.COST_STRSOUL);
                cost.setStrSoul(i);
            } else if ((m & LogConstants.COST_REFSOUL) > 0) {
                m = (short) (m & ~LogConstants.COST_REFSOUL);
                cost.setRefSoul(i);
            } else if ((m & LogConstants.COST_SOULSTONE) > 0) {
                m = (short) (m & ~LogConstants.COST_SOULSTONE);
                cost.setSoulStone(i);
            } else if ((m & LogConstants.COST_AAMHID) > 0) {
                m = (short) (m & ~LogConstants.COST_AAMHID);
                cost.setAamhid(i);
            } else if ((m & LogConstants.COST_REALM) > 0) {
                m = (short) (m & ~LogConstants.COST_REALM);
                cost.setRealm(i);
            }
        }
    }