描述

本文先反编译枚举，再使用枚举实现单例

枚举

public enum EnumDemo {

    RED("red"),BLUE("blue"),PURPLE("purple");

    private String dest;

    EnumDemo(String dest) {
        this.dest = dest;
    }

    public static void getColor() {
        return;
    }
}

java -jar cfr-0.146.jar EnumDemo.class --sugarenums false

/*
 * Decompiled with CFR 0.146.
 */
package com.redoor.singleton;

public final class EnumDemo
extends Enum<EnumDemo> {
    public static final /* enum */ EnumDemo RED = new EnumDemo("RED", 0, "red");
    public static final /* enum */ EnumDemo BLUE = new EnumDemo("BLUE", 1, "blue");
    public static final /* enum */ EnumDemo PURPLE = new EnumDemo("PURPLE", 2, "purple");
    private String dest;
    private static final /* synthetic */ EnumDemo[] $VALUES;

    public static EnumDemo[] values() {
        return (EnumDemo[])$VALUES.clone();
    }

    public static EnumDemo valueOf(String name) {
        return Enum.valueOf(EnumDemo.class, name);
    }

    private EnumDemo(String string, int n, String dest) {
        super(string, n);
        this.dest = dest;
    }

    static {
        $VALUES = new EnumDemo[]{RED, BLUE, PURPLE};
    }
}

单例

单例源码

public enum Singleton {

    INSTANCE;

    private final Student student;

    Singleton() {
        student = new Student();
    }

    private Student getStudent() {
        return student;
    }

    public static Student getInstance() {
        return Singleton.INSTANCE.getStudent();
    }
}

单例反编译

java -jar cfr-0.146.jar Singleton.class --sugarenums false

/*
 * Decompiled with CFR 0.146.
 *
 * Could not load the following classes:
 *  com.redoor.singleton.Student
 */
package com.redoor.singleton;

import com.redoor.singleton.Student;

public final class Singleton
extends Enum<Singleton> {
    public static final /* enum */ Singleton INSTANCE = new Singleton("INSTANCE", 0);
    private final Student student = new Student();
    private static final /* synthetic */ Singleton[] $VALUES;

    public static Singleton[] values() {
        return (Singleton[])$VALUES.clone();
    }

    public static Singleton valueOf(String name) {
        return Enum.valueOf(Singleton.class, name);
    }

    private Singleton(String string, int n) {
        super(string, n);
    }

    private Student getStudent() {
        return this.student;
    }

    public static Student getInstance() {
        return INSTANCE.getStudent();
    }

    static {
        $VALUES = new Singleton[]{INSTANCE};
    }
}

引用

http://www.benf.org/other/cfr/how-are-enums-implemented.html
http://www.jetchen.cn/java-singleton-enum/