Android int二进制32位合并多个参数

与运算（&）：同1为1
例如：0&0=0；0&1=0；1&0=0；1&1=1

或运算（|）：有1为1
例如：0|0=0； 0|1=1；1|0=1；1|1=1；

异或运算（^）：不同为1
例如：0^0=0； 0^1=1；10=1；1^1=0；

取反(~)：二进制中1变0；0变1
例如：二进制1010；取反后就是0101

Integer.toBinaryString(int)：将整型值转换成二进制字符串

int最大值是2的31次方减1=2147483647，用二进制表示就是32个1，每一位上都可以用1和0来表示开关的状态；所以一个int值最多可以存储32个开关的状态，可以达到节约内存和提高性能的目的

package com.example.myapplication.binaryint;


class BinaryIntTest {
    private static final int FLAG_IN_USE = 1 << 0;
    private static final int FLAG_OTHER = 1 << 1;
    private static final int FLAG_OTHER1 = 1 << 2;
    private static final int FLAG_OTHER2 = 1 << 3;
    private static final int FLAG_OTHER3 = 1 << 4;
    private int flags;

    public void setFlagValue(boolean isUse, int flag) {
        if (isUse) {//开关位设置位1
            flags |= flag;
        } else {//开关位设置位0
            flags &= ~flag;
        }
        System.out.println(Integer.toBinaryString(flags));
    }

    public static void main(String[] args) {
        BinaryIntTest test = new BinaryIntTest();
        System.out.println(Integer.toBinaryString(test.flags));
        test.setFlagValue(true, FLAG_IN_USE);
        test.setFlagValue(true, FLAG_OTHER);
        test.setFlagValue(true, FLAG_OTHER1);
        test.setFlagValue(true, FLAG_OTHER2);
        test.setFlagValue(true, FLAG_OTHER3);

        test.setFlagValue(false, FLAG_OTHER2);
    }
}

运行结果：

0
1
11
111
1111
11111
10111

Process finished with exit code 0

Android中很多地方都用到了这种方式，比如MeasureSpec、Message等；

MeasureSpec是前2位用来记录mode，后30位记录size

package com.example.myapplication.binaryint;

import java.security.PublicKey;
class BinaryIntTest {
    static class MeasureSpec {
        private int measureSpec;
        private static final int MODE_SHIFT = 3 << 30;//3二进制表示11，左移30位后表示前两位是11，后30位都是0
        static final int UNSPECIFIED = 0 << 30;//00,左移30位
        static final int EXACTLY = 1 << 30;//01,左移30位
        static final int AT_MOST = 2 << 30;//10,左移30位

        public int getMode() {
            return measureSpec & MODE_SHIFT;
        }

        public int getSize() {
            return measureSpec & ~MODE_SHIFT;
        }

        public int makeMeasureSpec(int mode, int size) {
            measureSpec = 0;
            measureSpec |= mode;
            measureSpec |= size;
            return measureSpec;
        }

        public void setMode(int mode) {
            int size = getSize();
            measureSpec = 0;
            makeMeasureSpec(mode, size);
        }

        public void setSize(int size) {
            int mode = getMode();
            measureSpec = 0;
            makeMeasureSpec(mode, size);
        }

        public String getModeName() {
            String modeName = "未知";
            switch (getMode()) {
                case MeasureSpec.AT_MOST:
                    modeName = "AT_MOST";
                    break;
                case MeasureSpec.EXACTLY:
                    modeName = "EXACTLY";
                    break;
                case MeasureSpec.UNSPECIFIED:
                    modeName = "UNSPECIFIED";
                    break;
            }
            return modeName;
        }
    }

    public static void main(String[] args) {
        MeasureSpec measureSpec = new MeasureSpec();
        measureSpec.makeMeasureSpec(MeasureSpec.UNSPECIFIED, 1080);
        System.out.println(Integer.toBinaryString(measureSpec.getMode()) + "=>" + measureSpec.getModeName());
        System.out.println(Integer.toBinaryString(measureSpec.getSize()) + "=>" + measureSpec.getSize());

        System.out.println("修改后=》》》》》》》");
        measureSpec.setMode(MeasureSpec.AT_MOST);
        measureSpec.setSize(1920);
        System.out.println(Integer.toBinaryString(measureSpec.getMode()) + "=>" + measureSpec.getModeName());
        System.out.println(Integer.toBinaryString(measureSpec.getSize()) + "=>" + measureSpec.getSize());
    }
}

运行结果：

0=>UNSPECIFIED
10000111000=>1080
修改后=》》》》》》》
10000000000000000000000000000000=>AT_MOST
11110000000=>1920

Process finished with exit code 0