java位元運算筆記

標籤：java   位元運算   

位元運算：
~（非）——》位元進行0和1的互換

例子：

public class Test {public static void main(String[] args) {System.out.println(~-2);//輸出1System.out.println(~-1);//輸出0System.out.println(~0);//輸出-1System.out.println(~1);//輸出-2System.out.println(~2);//輸出-3System.out.println(~3);//輸出-4}}

^（異或）——》12 ^ 10 = ...01100^01010 =  00110 = 6

例子：

public class Test {public static void main(String[] args) {int a = 0;int b = 0;b = a = 12^10;System.out.println(a);//輸出為 6a = a^12;System.out.println(a);//輸出為 10b = b^10;System.out.println(b);//輸出為 12}}

應用：二個不同的數進行交換

public class Test {public static void main(String[] args) {int a = 12;int b = 10;System.out.println(a + "---" + b);// 輸出為12---10a = a ^ b;b = a ^ b;a = a ^ b;System.out.println(a + "---" + b);// 輸出為10---12}}

&（與）——》12 & 10 = ...01100 & 01010 = 01000 = 8

例子：

public class Test {public static void main(String[] args) {int a = 12;int b = 10;int c = a&b;System.out.println(c);//輸出為 8}}

應用：

public class Test {public static void main(String[] args) {int[] a = new int[2];a[0] = 5;a[1] = 6;for (int i = 0; i < a.length; i++) {if ((a[i] & 1) == 1) {// 判斷是否為奇數System.out.println(a[i] + "奇數");} else {System.out.println(a[i] + "偶數");}}// 輸出為：// 5"奇數"// 6"偶數"}}

|（或）——》12 | 10 = ...01100 | ...01010 = 01110 = 14

例子：

public class Test {public static void main(String[] args) {int a = 12;int b = 10;// ...01100 | ...01010 = 01110 = 14int c = a | b;System.out.println(c);// 輸出為14}}

應用：和位移一起運算可以打包成不同位元的整數

public class Test {public static void main(String[] args) {int a = 1;int b = 2;// 256 | 2 = ...01 0000 0000 | ...0010 = ...01 0000 0010 = 258int c = a << 8 | b;System.out.println(c);// 輸出為258}}

>>（右位移）——》12>>2 = 00...01100 >>2 = 00...00011 = 3

-1 >>>24 = 1111...111 >>>24 = 1111...1111 1111 = -1
>>>（無符號）——》 -1 >>> 24 = 1111...111 >>> 24 = 0000...1111 1111 = 255

public class Test {public static void main(String[] args) {int a = -1;// 1111...111 >>> 24 = 0000...1111 1111 = 255int b = a>>>24;System.out.println(b);// 輸出為255}}

12>>2 = 00...01100 >>2 = 00...00011 = 3

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java位元運算筆記