Thread: Stack implementation and shallow copy

Im new the the shallow copy/deep copy concept. I need a little help understanding whats actually going on in this implementation:

public class Stack1 {
 
private Object value;
private Stack1 rest;
private boolean empty;
public boolean isEmpty() { return empty; }
 
public Stack1() { 
value = null;
rest = null;
empty = true;
}
 
private Stack1(Stack1 other){ //Make fields of this object point to the same objects in another stack's fields i.e. shallow copy
this.value = other.value;
this.rest = other.rest;
this.empty = other.empty;
}
 
public void push(Object x){
this.rest = new Stack1(this); //What's going on here?
this.value = x;
this.empty = false; 
}

In the push method we make a shallow copy on the RHS which means that there is some object whose fields are referencing the same memory blocks as our current stack object (this). But we then go ahead and say, ok now take our current object (this) and set its rest to be this copy. But this.rest has just been altered, doesn't that mean the object copy's rest will be referencing itself? so its like some kind of infinite loop now???

HELP!

Thanks

Am I thinking about this wrong?... is it only if I alter the object its referencing (using mutator methods) rather than the variable holding the reference? I think this might be my issue.. so if I did something like

this.rest.pop()

then a clone would also have its rest popped?

but if i went this.rest = new Object()

then the clones rest would still be the old this.rest?