how to implement generic array list copy constructor?

Question

import java.util.ArrayList;

public class MyStack<T> {

private ArrayList<T> stack;

    // Copy constructor
    public MyStack(MyStack<T> s) {

        // i know its wrong
        for(int i = 0; i < stack.size(); i++) {
           this.stack.get(i) = s.stack.get(i);
        }
    }
}

the class is generic MyStack<T> as well as ArrayList<T> idk y its not showing it — user2877264
– user2877264, Commented Oct 14, 2013 at 0:24
Just for future reference @user2877264 - this code won't successfully compile, because a retrieval can't be used as an assignment target, only a variable can. — Clockwork-Muse
– Clockwork-Muse, Commented Oct 14, 2013 at 0:53

Peter Lawrey · Accepted Answer · 2013-10-14 00:13:40Z

3

How about

// Copy constructor
public MyStack(MyStack<T> s) {
    this.stack = new ArrayList<T>(s.stack);    
}

answered Oct 14, 2013 at 0:13

Peter Lawrey

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7 Comments

user2877264 Over a year ago

but its private ArrayList<T> stack; i need to copy all the elements

Peter Lawrey Over a year ago

This will copy all the reference to elements in the stack. What is your doubt? What happened when you tried it?

user2877264 Over a year ago

i did it this way this.stack = new ArrayList<T>(); for(int i = 0; i < stack.size(); i++) { this.stack.add(s.stack.get(i)); }

user2877264 Over a year ago

is it the same thing ?

Peter Lawrey Over a year ago

@user2877264 It is basically the same, just longer. You can look at the Javadoc or code for the constructor to see for yourself.

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newtonrd · Accepted Answer · 2013-10-14 00:13:38Z

0

Have you tried to debug at all? An obvious suggestion would be to make sure that you're referencing the correct stack.

answered Oct 14, 2013 at 0:13

newtonrd

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2 Comments

Peter Lawrey Over a year ago

Possibly a comment rather than an answer, but I doubt it compiles so you can't debug it.

newtonrd Over a year ago

This should have been a comment. My mistake

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