每次在对象的序列化之前和序列化之后获得相同的哈希码，而不使用Java中的readResolve方法，为什么？

Question

Getting same Hashcode every time before serialization and after deserialization of object without using readResolve() method in Java why ? Here is my class

public class SerializedSingletonClass implements Serializable{

    private static final long serialVersionUID = 18989987986l;

    private SerializedSingletonClass(){};

    private static class InstanceHelper {
        private static SerializedSingletonClass obj = new   SerializedSingletonClass();
    }

    public static SerializedSingletonClass getInstance(){
        return InstanceHelper.obj;
    }
}

Test Class --

public class TestSingleton {
public static void main(String[] args) throws FileNotFoundException,
        IOException, ClassNotFoundException {
    // Test Serialization for singleton pattern
            SerializedSingletonClass instanse1 = SerializedSingletonClass
                    .getInstance();
            ObjectOutputStream obs = new ObjectOutputStream(new FileOutputStream(
                    "filename1.ser"));
            obs.writeObject(instanse1);
            obs.close();
            ObjectInputStream objInputStream = new ObjectInputStream(
                    new FileInputStream("filename1.ser"));
            SerializedSingletonClass instance2 = (SerializedSingletonClass) objInputStream
                    .readObject();
            objInputStream.close();
            System.out.println("instance1==" + instanse1.getClass().hashCode());
            System.out.println("instance2==" + instance2.getClass().hashCode());
}

}

Output ::

instance1==1175576547

instance2==1175576547

Answer 1

Your objects are instances of the same class, SerializedSingletonClass. You're getting the hashCode from the class, not from the instance. instanse1.getClass() evaluates to the same thing as instance2.getClass() , so of course they produce the same hashCode.

To find the hashCode of the objects, use instanse1.hashCode() and instance2.hashCode() .