java 位操作 bitwise(按位) operation bit

java 位操作 bitwise(按位) operation bit

//一篇对于 原码 反码 补码 的介绍
http://www.cnblogs.com/zhangziqiu/archive/2011/03/30/ComputerCode.html
java中有三种移位运算符

<< : 左移运算符，num << 1,相当于num乘以2

>> : 右移运算符，num >> 1,相当于num除以2

>>> : 无符号右移，忽略符号位，空位都以0补齐

// 8 0000 0000 0000 1000 原码
　 1111 1111 1111 0111 反码

+　　　　　　　　　　　　 1

　　　1111 1111 1111 1000 （8的补码）来表示 -8

// -8 1111 1111 1111 1000 65528 补码（正值 的反码+1）

// 65535 1111 1111 1111 1111 65535
// 65535-65528=7+1=8

操作longValue = longValue | (1 << n); 可以在longValue的2进制表示中，把从右边数到左边数第n + 1位的值设置为1，并且不影响其他位上面的值 即用0和2进制值变量x做或|or操作，不会影响到2进制变量x的值

操作longValue = longValue & ~(1 << n); 可以在longValue的2进制表示中，把从右边数到左边数第n + 1位设置为0，并且不影响其他位上面的值 即用1和2进制值变量x做与&and操作，不会影响到2进制变量x的值

操作System.out.println((longValue >> n & 1) == 1); 可以判断值longValue的2进制表示中，从右边数到左边第n + 1位的值是0false 还是1true

Java代码


public class bitOperation {

/**

* @param args

*/

public static void main(String[] args) {

long longValue = 0;

longValue = longValue | (1 << 0);

// 1

System.out.println(Long.toBinaryString(longValue));

longValue = longValue | (1 << 1);

// 11

System.out.println(Long.toBinaryString(longValue));

longValue = longValue | (1 << 4);

// 10011

System.out.println(Long.toBinaryString(longValue));

longValue = longValue | (1 << 5);

// 110011

System.out.println(Long.toBinaryString(longValue));

longValue = longValue | (1 << 6);

// 1110011

System.out.println(Long.toBinaryString(longValue));

String hex = Long.toBinaryString(longValue);

// 1110011

System.out.println(hex);

// 115

System.out.println(Integer.valueOf("1110011", 2));

// 1110011

System.out.println(Long.toBinaryString(longValue >> 0));

// 1

System.out.println(Long.toBinaryString(longValue >> 0 & 1));

// 111001

System.out.println(Long.toBinaryString(longValue >> 1));

// 1

System.out.println(Long.toBinaryString(longValue >> 1 & 1));

// true

System.out.println((longValue >> 0 & 1) == 1);

// true

System.out.println((longValue >> 1 & 1) == 1);

// false

System.out.println((longValue >> 2 & 1) == 1);

// false

System.out.println((longValue >> 3 & 1) == 1);

// true

System.out.println((longValue >> 4 & 1) == 1);

// true

System.out.println((longValue >> 5 & 1) == 1);

// true

System.out.println((longValue >> 6 & 1) == 1);

// false

System.out.println((longValue >> 7 & 1) == 1);

// Demonstrate the bitwise logical operators.

bitLogic();

// Left shifting a byte value.

byteShift();

}

/**

* Left shifting a byte value.

*/

private static void byteShift() {

byte a = 64, b;

int i;

i = a << 2;

b = (byte) (a << 2);

// Original value of a: 64

System.out.println("Original value of a: " + a);

// i and b: 256 0

System.out.println("i and b: " + i + " " + b);

System.out.println("\r\n");

}

/**

* Demonstrate the bitwise logical operators.

*/

private static void bitLogic() {

String binary[] = { "0000", "0001", "0010", "0011", "0100", "0101",

"0110", "0111", "1000", "1001", "1010", "1011", "1100", "1101",

"1110", "1111"

};

int a = 3; // 0 + 2 + 1 or 0011 in binary

int b = 6; // 4 + 2 + 0 or 0110 in binary

int c = a | b;

int d = a & b;

int e = a ^ b;

int f = (~a & b) | (a & ~b);

int g = ~a & 0x0f;

// a = 0011 = 3

System.out.println(" a = " + binary[a] + " = " + a);

// b = 0110 = 6

System.out.println(" b = " + binary[b] + " = " + b);

// a|b = 0111 = 7

System.out.println(" a|b = " + binary[c] + " = " + c);

// a&b = 0010 = 2

System.out.println(" a&b = " + binary[d] + " = " + d);

// a^b = 0101 = 5

System.out.println(" a^b = " + binary[e] + " = " + e);

// ~a&b|a&~b = 0101 = 5

System.out.println("~a&b|a&~b = " + binary[f] + " = " + f);

// ~a = 1100 = 12

System.out.println(" ~a = " + binary[g] + " = " + g);

System.out.println("\r\n");

}

}