How to Obtain the Java Object Reference When toString() and hashCode() Are Overridden?

How can I print the object reference of an object in Java when both toString() and hashCode() methods have been overridden?

public class MyClass {
    @Override
    public String toString() {
        return "CustomStringRepresentation";
    }
    
    @Override
    public int hashCode() {
        return 42;
    }
}

When working with Java objects, particularly in debugging scenarios within multi-threaded applications, it can be challenging to verify the identity and uniqueness of an object when its `toString()` and `hashCode()` methods have been overridden. This guide provides techniques to retrieve the underlying object reference, ensuring you can effectively validate instances of your objects.

// Example demonstrating how to print the object reference using identityHashCode
MyClass obj = new MyClass();
System.out.println("Object reference: " + System.identityHashCode(obj));
System.out.println("Object class name: " + obj.getClass().getName());

Causes

• Overriding `toString()` can prevent you from obtaining the default representation which includes the object reference.
• Overriding `hashCode()` affects the hashing mechanism used in collections, making it harder to establish identity through hash-based structures.

Solutions

• Use the `System.identityHashCode(Object)` method, which retrieves the hash code of the object based on its identity rather than its content.
• You can print the object reference by utilizing a special print method that invokes the object directly when debugging.
• Employ the `Object.getClass().getName()` method combined with the identity hash code to better understand the object's identity.

Mistake: Assuming `toString()` returns a memory address or identifier.

Solution: Remember that `toString()` is meant for human-readable representation; use `System.identityHashCode()` instead.

Mistake: Not considering the implications of `hashCode()` in collection classes.

Solution: Be aware that overriding `hashCode()` alters how Java will recognize an object's identity in hash-based collections.