The heck?


Type1[][] backup = (Type1[][])this.original.clone();

/*
 * Some processing going on in original array
 *
 *
 * For debugging purposes I check backup and it has change
 */

this.original = backup; //no that important; backup changed before this

Can anybody hint out what's happening. I didn't touch backup in the whole processing. Isn't clone supposed to create new clone instead of just copying over the reference variable? Or do I perhaps need to override clone() with a custom method because perhaps it doesn't work properly with custom types (such as type1 above)? Or am I just talking bunkers?   I

public class Test {
    public static void main(String[] args) {
        Wheel w1 = new Wheel(5);
        Wheel w2 = new Wheel(10);
       
        Motorcycle m1 = new Motorcycle(w1, w2);
        Motorcycle m2 = m1.correctClone();
        m2.frontWheel.radius = 3;
        System.out.println(m1.frontWheel.radius); //Prints 5, m1.frontWheel is not the same as m2.frontWheel
       
        Motorcycle m3 = m1.incorrectClone();
        m3.frontWheel.radius = 3;
        System.out.println(m1.frontWheel.radius); //Prints 3, m1.frontWheel is the same as m2.frontWheel
    }
}
class Motorcycle {
    public Wheel frontWheel, backWheel;
    public Motorcycle(Wheel front, Wheel back) {
        this.frontWheel = front;
        this.backWheel = back;
    }
    public Motorcycle correctClone() {
        return new Motorcycle(frontWheel.clone(), backWheel.clone());
    }
    public Motorcycle incorrectClone() {
        return new Motorcycle(frontWheel, backWheel);
    }
}
class Wheel {
    public int radius;
    public Wheel(int radius) {
        this.radius = radius;
    }
    public Wheel clone() {
        return new Wheel(this.radius);
    }
}

>>1
You have an array of references to arrays of references to objects.

When you clone your array of references you get a new array of references. Which still refer to the same old arrays of references to the same old objects.

In other words, clone() usually performs a shallow copy.