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import java.lang.reflect.Constructor;public class SingletonTest {    public static void main(String[] args) {        Singleton singleton = Singleton.getSingleton();        try {            Class
     singletonClass = Singleton.class;            Constructor
     constructor = singletonClass.getDeclaredConstructor(null);            constructor.setAccessible(true);            Singleton singletonByReflect = constructor.newInstance();            System.out.println("singleton : " + singleton);            System.out.println("singletonByReflect : " + singletonByReflect);            System.out.println("singleton == singletonByReflect : " + (singleton == singletonByReflect));        } catch (Exception e) {            e.printStackTrace();        }    }}

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public class SingletonTest {    public static void main(String[] args) {        Singleton singleton = Singleton.getSingleton();        try {            ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("tempFile"));            oos.writeObject(singleton);            ObjectInputStream ois = new ObjectInputStream(new FileInputStream("tempFile"));            Singleton singletonBySerialize = (Singleton) ois.readObject();            System.out.println("singleton : " + singleton);            System.out.println("singletonBySerialize : " + singletonBySerialize);            System.out.println("singleton == singletonBySerialize : " + (singleton == singletonBySerialize));        } catch (Exception e) {            e.printStackTrace();        }    }}

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private Singleton() {    if (singleton != null) {        throw new RuntimeException("Singleton constructor is called...");    }}

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?? readResolve ??

private Object readResolve() {    return getSingleton();}

????????????? readResolve ???????????????????????????