JAVA操作符位移详解

package util;

public class BitOperator {

    public static void main(String[] args) {
        System.out.println("\n按位左移");
        output("123", 123);
        output("123 > 2", 123 >> 2);
        System.out.println("\n按位有符号右移，右移时高位补充符号位");
        output("-123", -123);
        output("-123 >> 2", -123 >> 2);

        System.out.println("\n按位无符号右移");
        output("123", 123);
        output("123 >>> 1", 123 >>> 1);

        System.out.println("\n按位无符号右移，右移时高位补 0");
        output("-123", -123);
        output("-123 >>> 2", -123 >>> 2);
    }

    private static void output(String prompt, int result) {
        System.out.printf("%10s = %-10d  %s%n", prompt, result, toBit(result));
    }

    public static String toBit(int num) {
        char[] chs = new char[39];
        for (int i = 0, k = 0; i < Integer.SIZE; i++) {
            chs[k++] = (char)('0'+ ((num >>> Integer.SIZE - i - 1) & 1));
            if ((i & 3) == 3 && k < chs.length) {
                chs[k++] = ' ';
            }
        }
        return new String(chs);
    }
}


/*
  按位左移
 
       123 = 123         0000 0000 0000 0000 0000 0000 0111 1011
  123 > 2 = 30          0000 0000 0000 0000 0000 0000 0001 1110

按位有符号右移，右移时高位补充符号位
      -123 = -123        1111 1111 1111 1111 1111 1111 1000 0101
 -123 >> 2 = -31         1111 1111 1111 1111 1111 1111 1110 0001

按位无符号右移
       123 = 123         0000 0000 0000 0000 0000 0000 0111 1011
 123 >>> 2 = 30          0000 0000 0000 0000 0000 0000 0001 1110

按位无符号右移，右移时高位补 0
      -123 = -123        1111 1111 1111 1111 1111 1111 1000 0101
-123 >>> 2 = 1073741793  0011 1111 1111 1111 1111 1111 1110 0001
*/