检查设置清除和切换各个位。使用长位掩码

假设我们要修改整数原语的 n，i（byte，short，char，int 或 long）：

(i & 1 << n) != 0 // checks bit 'n'
i |= 1 << n;      // sets bit 'n' to 1
i &= ~(1 << n);   // sets bit 'n' to 0
i ^= 1 << n;      // toggles the value of bit 'n'

使用 long / int / short / byte 作为位掩码：

public class BitMaskExample {
    private static final long FIRST_BIT = 1L << 0;
    private static final long SECOND_BIT = 1L << 1;
    private static final long THIRD_BIT = 1L << 2;
    private static final long FOURTH_BIT = 1L << 3;
    private static final long FIFTH_BIT = 1L << 4;
    private static final long BIT_55 = 1L << 54;

    public static void main(String[] args) {
        checkBitMask(FIRST_BIT | THIRD_BIT | FIFTH_BIT | BIT_55);
    }

    private static void checkBitMask(long bitmask) {
        System.out.println("FIRST_BIT: " + ((bitmask & FIRST_BIT) != 0));
        System.out.println("SECOND_BIT: " + ((bitmask & SECOND_BIT) != 0));
        System.out.println("THIRD_BIT: " + ((bitmask & THIRD_BIT) != 0));
        System.out.println("FOURTh_BIT: " + ((bitmask & FOURTH_BIT) != 0));
        System.out.println("FIFTH_BIT: " + ((bitmask & FIFTH_BIT) != 0));
        System.out.println("BIT_55: " + ((bitmask & BIT_55) != 0));
    }
}

打印

FIRST_BIT: true
SECOND_BIT: false
THIRD_BIT: true
FOURTh_BIT: false
FIFTH_BIT: true
BIT_55: true

它匹配我们作为 checkBitMask 参数传递的掩码：FIRST_BIT | THIRD_BIT | FIFTH_BIT | BIT_55。