How to print the address of an object if you have redefined toString method

Question

I'm a newbie to Java. Now I'm studying equals and == and redefinition of equals and toString.

I would like to use both the toString method that I have redefied and the default method that is inherited from the Object class.

I failed to use that super modificator to reach that method.

This is for educational purposes only. What I would like to get is more clear if you will have a look at the comments in my code.

Could you help me here?

My code is:

public class EqualTest{
    public static void main(String[] args){ 
        Employee alice1 = new Employee("Alice Adams", 75000, 1987, 12, 15);
            //System.out.super.println(alice1);

        Employee alice2 = alice1;
            //System.out.super.println(alice2);

        Employee alice3 = new Employee("Alice Adams", 75000, 1987, 12, 15);
            //System.out.super.println(alice3);

        System.out.println("alice1==alice2: " + (alice1==alice2));
        System.out.println("alice1 == alice3: " + (alice1==alice3));
        System.out.println("alice1.equals(alice3): " + alice1.equals(alice3));
    }
}

class Employee{
...
    public String toString(){
        return getClass().getName() + "[name = " + name + 
            ", salary=" + salary + ", hireDay=" + hireDay + "]";
    }

}

Answer 1

If you want to achieve sort-of default toString() behavior, you can make use of System.identityHashCode() method. Default toString() will then look like this:

public String toString(Object o) {
    return o.getClass().getName() + "@" + 
           Integer.toHexString(System.identityHashCode(o));
}

Answer 2

You can call super() method to execute the corresponding superclass method.

class Employee{
...
    public String toString(){
         String s = super.toString();
        return getClass().getName() + "[name = " + name + 
            ", salary=" + salary + ", hireDay=" + hireDay + "]" + s;
    }

toString() in Object class is as follows

public String toString() {
    return getClass().getName() + "@" + Integer.toHexString(hashCode());
}

Answer 3

Here is an in-depth answer about overriding equals and hashcode

What issues should be considered when overriding equals and hashCode in Java?

The key point being The relation between the two methods is:

Whenever a.equals(b), then a.hashCode() must be same as b.hashCode().

Answer 4

You may create another method inside your Employee class to use super toString method.

See example:

public class Employee {
    public String toString() {
        return "MyToStringMethod";
    }

    public String superToString() {
        return super.toString();
    }

    public static void main(String[] args) {
        Employee b = new Employee();
        System.out.println(b);
        System.out.println(b.superToString());
    }
}

or combine both in one method:

public class Employee {
    public String toString() {
        return super.toString() + " MyToStringMethod";
    }

    public static void main(String[] args) {
        Employee b = new Employee();
        System.out.println(b);
    }
}