位运算&位掩码示例（权限）

 

参考资料地址：

1、https://juejin.cn/post/6844903909333401607

2、https://www.jianshu.com/p/78a984173985

3、【精华】《位运算（位掩码BitMask）的简单应用场景浅析》 https://www.jianshu.com/p/78a984173985

 

位掩码示例：

import org.apache.commons.lang3.StringUtils;

import com.google.common.collect.Lists;

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

/**
 * Hello world!
 *
 */
public class App {
    public static void main(String[] args) {

        System.out.println(String.format("%2s:%s", Perms.READ, toBinaryStringFormat(Perms.READ)));
        System.out.println(String.format("%2s:%s", Perms.WRITE, toBinaryStringFormat(Perms.WRITE)));
        System.out.println(String.format("%2s:%s", Perms.CREATE, toBinaryStringFormat(Perms.CREATE)));
        System.out.println(String.format("%2s:%s", Perms.DELETE, toBinaryStringFormat(Perms.DELETE)));
        System.out.println(String.format("%2s:%s", Perms.ADMIN, toBinaryStringFormat(Perms.ADMIN)));
        System.out.println(String.format("%2s:%s", Perms.ALL, toBinaryStringFormat(Perms.ALL)));
        System.out.println(String.format("%2s:%s", Perms.DENY_ALL, toBinaryStringFormat(Perms.DENY_ALL)));

        System.out.println(String.format("%s", StringUtils.repeat("=", 100)));

        Perms p = new Perms();
        p.setPermission(Perms.READ);
        System.out
                .println(String.format("%2s:%s", p.getPermission(), toBinaryStringFormat(p.getPermission())));
        p.enable(Perms.WRITE | Perms.CREATE);
        System.out
                .println(String.format("%2s:%s", p.getPermission(), toBinaryStringFormat(p.getPermission())));
        p.enable(Perms.ADMIN);
        System.out
                .println(String.format("%2s:%s", p.getPermission(), toBinaryStringFormat(p.getPermission())));

    }

    public static String toBinaryStringFormat(int perm) {
        String string = StringUtils.leftPad(Integer.toBinaryString(perm), Integer.SIZE, '0');
        List<List<String>> lists = Lists.partition(Arrays.asList(string.split("")), Byte.SIZE);
        return lists.stream().map(list -> {
            return String.join("", list);
        }).collect(Collectors.joining(" "));
    }

}

class Perms {
    /**
     * 00000000 00000000 00000000 00000001
     */
    public static final int READ = 1 << 0;
    /**
     * 00000000 00000000 00000000 00000010
     */
    public static final int WRITE = 1 << 1;
    /**
     * 00000000 00000000 00000000 00000100
     */
    public static final int CREATE = 1 << 2;
    /**
     * 00000000 00000000 00000000 00001000
     */
    public static final int DELETE = 1 << 3;
    /**
     * 00000000 00000000 00000000 00010000
     */
    public static final int ADMIN = 1 << 4;
    /**
     * 00000000 00000000 00000000 00011111
     */
    public static final int ALL = READ | WRITE | CREATE | DELETE | ADMIN;
    public static final int DENY_ALL = READ & WRITE & CREATE & DELETE & ADMIN;

    // 存储目前的权限状态
    private int flag;

    /**
     * 移除一项或多项权限
     */
    public void disable(int permission) {
        flag &= ~permission;
    }

    /**
     * 添加一项或多项权限
     */
    public void enable(int permission) {
        flag |= permission;
    }

    /**
     *
     * 得到当前权限
     */
    public int getPermission() {
        return flag;
    }

    /**
     * 是否拥有某项权限
     */
    public boolean isAllow(int permission) {
        return (flag & permission) == permission;
    }

    /**
     * 是否禁用了某些权限
     */
    public boolean isNotAllow(int permission) {
        return (flag & permission) == 0;
    }

    /**
     * 是否仅仅拥有某些权限
     */
    public boolean isOnlyAllow(int permission) {
        return flag == permission;
    }

    /**
     * 重新设置权限
     */
    public void setPermission(int permission) {
        flag = permission;
    }
}