Android使用注解代替枚举节省系统内存开销的方法

package com.yw.enumproxylib;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

import androidx.annotation.IntDef;

/**
 * 定义一个int类型的注解
 * 用注解代替枚举，做到类型安全
 * create by yangwei
 * on 2020-01-30 21:34
 */
public class EnumProxy {
  public static final int READ_CAR = 0;//红色的汽车
  public static final int GREEN_CAR = 1;//绿色的汽车
  public static final int YELLOW_CAR = 2;//黄色的汽车


  @IntDef({READ_CAR, GREEN_CAR, YELLOW_CAR})
  @Retention(RetentionPolicy.SOURCE)//源码级别
  public @interface CAR_Enum {

  }

  /**
   * 获取汽车类型
   *
   * @param car
   * @return
   */
  public static int getCar(@CAR_Enum int car) {
    switch (car) {
      case READ_CAR:
        return 0;
      case GREEN_CAR:
        return 1;
      case YELLOW_CAR:
        return 2;
    }
    return -1;
  }
}

package com.yw.enumproxylib;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

import androidx.annotation.StringDef;

/**
 * 定义一个string类型的注解，用于检查星期的类型安全。
 * create by yangwei
 * on 2020-01-30 22:04 week
 */
public class StringEnum {

  public static final String MOnDAY= "monday";
  public static final String TUESDAY = "tuesday";
  public static final String WENDESDAY = "wendesday";
  public static final String THURSDAY = "thursday";
  public static final String FRIDAY = "friday";
  public static final String SATURDAY = "saturday";
  public static final String WEEKDAY = "weekday";

  @StringDef({MONDAY, TUESDAY, WENDESDAY, THURSDAY, FRIDAY, SATURDAY, WEEKDAY})//此处定义注解的值只能是这几个
  @Retention(RetentionPolicy.SOURCE)//编译时注解，源码级检查
  public @interface Week {

  }

  /**
   * 获取日期
   *
   * @param week
   * @return
   */
  public static String getWeek(@Week String week) {
    switch (week) {
      case MONDAY:
        return "星期一";
      case TUESDAY:
        return "星期二";
      case WENDESDAY:
        return "星期三";
      case THURSDAY:
        return "星期四";
      case FRIDAY:
        return "星期五";
      case SATURDAY:
        return "星期六";
      case WEEKDAY:
        return "星期日";
    }
    return null;
  }
}

package com.yw.enumproxy;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

import com.yw.enumproxylib.EnumProxy;
import com.yw.enumproxylib.StringEnum;

/**
 * 测试例子
 */
public class MainActivity extends AppCompatActivity {

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    int car_black = 10;
    int bk = EnumProxy.getCar(car_black);//此处类型检查不通过
    int ck = EnumProxy.getCar(EnumProxy.GREEN_CAR);//类型检查通过


    String str = "friday";
    String week1 = StringEnum.getWeek(str);//直接赋值String时类型检查不通过
    String week2 = StringEnum.getWeek(StringEnum.FRIDAY);//赋值定义好的值时类型检查通过
  }
}