2018-11-30[Camille Wu] Singleton

[wwq0912]

Singleton2.java

public class Singleton2 implements Serializable {
    private static final long serialVersionUID = -5809782578272943999L;
    private static Singleton2 instance = null; //懒汉
    private  Singleton2() {
        if (instance != null) {
            throw new RuntimeException("Against Reflection");
        }
    }
    //Against multi-thread
    public synchronized static Singleton2 getSingleton2(String name) {
        if (null == instance) {
            instance = new Singleton2();
        }
        return instance;
    }

   private Object readResolve() throws ObjectStreamException {
        // Against Serizlization
        if (null == instance) {
            instance = new Singleton2();
        }
        return instance;
    }

}

Lazy.java

public class Lazy implements Runnable {
    private Thread t;
    private String threadName;

    Lazy(String name) {
        threadName = name;
    }

    public void run() {

        try {
            for (int i = 4; i > 0; i--) {
                Thread.sleep(50);
                Singleton2 test1 = Singleton2.getSingleton2();
                SerializeMethod(test1);
                Singleton2 test2 = DeserializeMethod();
                System.out.print("test Serizlization====");
                System.out.println(test1 == test2);
                testReflection(test1);
            }
        } catch (Exception e) {
            System.out.println("Thread " + threadName + " interrupted.");
        }
    }

    public void start() {
        if (t == null) {
            t = new Thread(this, threadName);
            t.start();
        }
    }

    public static void main(String args[]) {
        Lazy R1 = new Lazy("Thread-1");
        R1.start();
        Lazy R2 = new Lazy("Thread-2");
        R2.start();
    }
    private void testReflection(Singleton2 obj) {
        System.out.print("testReflection =====");
        try {
            Constructor<Singleton2> constructor = Singleton2.class.getDeclaredConstructor();
            constructor.setAccessible(true);
            Singleton2 obj2 = constructor.newInstance();
            System.out.print("testReflection result=====");
            System.out.println( obj == obj2);
        }catch (Exception e)  {
            System.out.println(e);
        }
    }

    public Singleton2 getObj() {
        Singleton2 test = Singleton2.getSingleton2();
        return test;
    }

    private static void SerializeMethod(Singleton2 objTemp) throws FileNotFoundException, IOException {
        ObjectOutputStream oo = new ObjectOutputStream(new FileOutputStream(new File("C:/122/Singleton.txt")));
        oo.writeObject(objTemp);
        oo.close();
    }

    private static Singleton2 DeserializeMethod() throws Exception, IOException {
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream(new File("C:/122/Singleton.txt")));
        Singleton2 singleton = (Singleton2) ois.readObject();
        return singleton;
    }
}