左乘右除
<<(向左位移)针对二进制，转换成二进制后(32位)向左边移动n位，相当于这个整数乘以2的n次方；
>>(向右位移)针对二进制，转换成二进制后(32位)向右移动n位,相当于这个整数除以2的n次方,正数高位补0, 正数高位补1；
>>> (无符号右移)
按二进制形式把所有的数字向右移动对应位数，低位移出(舍弃)，高位的空位补零。对于正数来说和带符号右移相同，对于负数来说不同。不管正负数高位都补0
不过这种方式只能用于乘以除以2的n次方，但是他的效率比乘法运算要高；
public class Main {public static void main(String[] args){int a = 0;a = 3 << 1;System.out.println("3 << 1 = "+a+" (相当于3*2)");a = 3 << 2;System.out.println("3 << 2 = "+a+" (相当于3*4)");int aa=1;aa <<= 2;System.out.println("a << 2 = "+aa+" (相当于a*4并将值付给aa)");int b = 0;b = 10 >> 1;System.out.println("10 >> 1 = "+b+" (相当于10/2)");b = 10 >> 2;System.out.println("10 >> 2 = "+b+" (相当于10/4)");System.out.println("3 >> 2 = "+(3>>2));System.out.println("3 >> 1 = "+(3>>1));System.out.println("5 >> 1 = "+(5>>1));}}
运算结果：
3 << 1 = 6 (相当于3*2)3 << 2 = 12 (相当于3*4)a << 2 = 4 (相当于a*4并将值付给aa)10 >> 1 = 5 (相当于10/2)10 >> 2 = 2 (相当于10/4)3 >> 2 = 03 >> 1 = 15 >> 1 = 2
int level=1; //1代表省级级别,2代表市级级别,3代表县级级别int userCode = 1 << (3-level); //位运算得到对应的二进制int access = Integer.parseInt("110", 2); //110代表省市有权限,县级无(将字符串转换成二进制)boolean canAccess = (userCode & access) > 0; //两个数字进行与运算以下是三种情况: 0000 0000 0000 0000 0000 0000 0000 0100 是level代表的值0000 0000 0000 0000 0000 0000 0000 0110 是设置的权限值0000 0000 0000 0000 0000 0000 0000 0100=4 省级0000 0000 0000 0000 0000 0000 0000 00100000 0000 0000 0000 0000 0000 0000 01100000 0000 0000 0000 0000 0000 0000 0010=2 市级0000 0000 0000 0000 0000 0000 0000 00010000 0000 0000 0000 0000 0000 0000 01100000 0000 0000 0000 0000 0000 0000 0000=0 县级
import mon.collect.Lists;import lombok.Getter;import java.util.HashMap;import java.util.List;import java.util.Map;/*** @author: lwh* @create: /7/23 19:14* @desc:*/@Getterpublic enum ResourcesTypeBitEnum {VIDEO("视频", 1<<1, 1),EXAM_PAPER("试卷", 1<<2, 2),FM("FM", 1<<3, 3),CAREER_NEWS("资讯", 1<<4, 4),PSYCHOLOGY_REPORT("板报", 1<<5, 5),FUN_TEST("测评", 1<<6, 6),EXERCISES("专题", 1<<7, 7);private String name;private Integer bitCode;private Integer code;ResourcesTypeBitEnum(String name, Integer bitCode, Integer code) {this.name = name;this.bitCode = bitCode;this.code = code;}/*** 所有的科目的枚举** @return*/public static Map<Integer, ResourcesTypeBitEnum> getMap() {Map<Integer, ResourcesTypeBitEnum> map = new HashMap<>();for (ResourcesTypeBitEnum e : ResourcesTypeBitEnum.values()) {map.put(e.getCode(), e);}return map;}/*** 位枚举转换为枚举对象** @param bitCode* @return*/public static List<ResourcesTypeBitEnum> bitEnum2enumCode(Long bitCode) {List<ResourcesTypeBitEnum> result = Lists.newArrayList();for (ResourcesTypeBitEnum e : ResourcesTypeBitEnum.values()) {if ((bitCode & e.getBitCode()) > 0L) {result.add(e);}}return result;}/*** 是否包含指定的类型** @param bitCode* @param bitEnum* @return*/public static boolean bitCodeContains(Long bitCode, ResourcesTypeBitEnum bitEnum) {if ((bitCode & bitEnum.getBitCode()) > 0) {return true;}return false;}public static void main(String[] args) {for (ResourcesTypeBitEnum value : ResourcesTypeBitEnum.values()) {System.out.println(value.getBitCode());}}}
