淺談java中的移動位運算：,&gt;&gt;&gt;

2024-07-14 08:43:55

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1. 概念

<< 左移運算符，左移是在后面補0， num << 1,相當于num乘以2
>> 右移運算符, 右移是在前面補1或0，num >> 1, 相當于num除以2
>>> 無符號右移，是在前面補0，忽略符號位，空位都以0補齊
另外，不論是左右還是右移32位，相當于不移動，還是原值。

實際上在java虛擬機執行這句代碼的時候如下這樣執行的：
5>>(n%32)--->結果
你這里n=32 ；所以5>>32即是 5>>(32%32)-->5>>0 的結果；

2. 測試代碼

public class Test{ public Test(){ System.out.println("=============算術右移 >> ==========="); int i=0xC0000000; System.out.println("移位前：i= "+i+" = "+Integer.toBinaryString(i)+"(B)"); i=i>>28; System.out.println("移位后：i= "+i+" = "+Integer.toBinaryString(i)+"(B)");  System.out.println("---------------------------------");  int j=0x0C000000; System.out.println("移位前：j= "+j+" = "+Integer.toBinaryString(j)+"(B)"); j=j>>24; System.out.println("移位后：j= "+j+" = "+Integer.toBinaryString(j)+"(B)");  System.out.println("/n"); System.out.println("==============邏輯右移 >>> ============="); int m=0xC0000000; System.out.println("移位前：m= "+m+" = "+Integer.toBinaryString(m)+"(B)"); m=m >>> 28; System.out.println("移位后：m= "+m+" = "+Integer.toBinaryString(m)+"(B)");  System.out.println("---------------------------------");  int n=0x0C000000; System.out.println("移位前：n= "+n+" = "+Integer.toBinaryString(n)+"(B)"); n=n>>24; System.out.println("移位后：n= "+n+" = "+Integer.toBinaryString(n)+"(B)");  System.out.println("/n"); System.out.println("==============移位符號的取模==============="); int a=0xCC000000; System.out.println("移位前：a= "+a+" = "+Integer.toBinaryString(a)+"(B)"); System.out.println("算術右移32：a="+(a>>32)+" = "+Integer.toBinaryString(a>>32)+"(B)"); System.out.println("邏輯右移32：a="+(a>>>32)+" = "+Integer.toBinaryString(a>>>32)+"(B)");  System.out.println("算術右移64：a="+(a>>64)+" = "+Integer.toBinaryString(a>>64)+"(B)"); System.out.println("邏輯右移64：a="+(a>>>64)+" = "+Integer.toBinaryString(a>>>64)+"(B)");  }  public static void main(String[] args){ new Test(); } }

運行結果：

=============算術右移 >> ===========
移位前：i= -1073741824 = 11000000000000000000000000000000(B)
移位后：i= -4 = 11111111111111111111111111111100(B)

移位前：j= 201326592 = 1100000000000000000000000000(B)
移位后：j= 12 = 1100(B)

==============邏輯右移 >>> =============
移位前：m= -1073741824 = 11000000000000000000000000000000(B)
移位后：m= 12 = 1100(B)

移位前：n= 201326592 = 1100000000000000000000000000(B)
移位后：n= 12 = 1100(B)

==============移位符號的取模===============
移位前：a= -872415232 = 11001100000000000000000000000000(B)
算術右移32：a=-872415232 = 11001100000000000000000000000000(B)
邏輯右移32：a=-872415232 = 11001100000000000000000000000000(B)
算術右移64：a=-872415232 = 11001100000000000000000000000000(B)
邏輯右移64：a=-872415232 = 11001100000000000000000000000000(B)