反射单例

package com.mycon.app;

import java.lang.reflect.Constructor;
import java.util.Arrays;

public class SingletonTest {

    @SuppressWarnings("rawtypes")
    public static void main(String[] args) {
        Singleton singleton = Singleton.getInstance();
        System.out.println(singleton.getName());
        Singleton s2 = null;
        try {
            Constructor[] constructors = Singleton.class.getDeclaredConstructors();
            System.out.println(constructors.length);
            for (Constructor c : constructors) {
                System.out.println(c.getName());
                Class[] params = c.getParameterTypes();
                System.out.println("Class params:" + Arrays.toString(params));
                if (params.length == 1) {　　　　　　　　　　　　// 取消语法检查
                    c.setAccessible(Boolean.TRUE);
                    s2 = (Singleton)c.newInstance(new Object[]{"Swift"});
                    break;
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println("s2:" + s2);
        System.out.println("s2-name:" + s2.getName());
        System.out.println("s1-name:" + singleton.getName());
    }
}　　　　

package com.mycon.app;

public class Singleton {

    private String name;

    private Singleton(String name) {
        this.name = name;
    }

    public static Singleton getInstance() {
        return SingletonHolder.SINGLETON_HOLDER;
    }

    private static class SingletonHolder {
        public static final Singleton SINGLETON_HOLDER = new Singleton("Jack");
    }

    public String getName() {
        return name;
    }
}

ouput:

Jack
2
com.mycon.app.Singleton
Class params:[class java.lang.String, class com.mycon.app.Singleton]
com.mycon.app.Singleton
Class params:[class java.lang.String]
s2:[email protected]
s2-name:Swift
s1-name:Jack