How do I copy a stack in Java?

Question

I have a stack A and I want to create a stack B that is identical to stack A. I don\'t want stack B to simply be a pointer to A -- I actually want to create a new stack B th

Answer 1

Just use the clone() -method of the Stack-class (it implements Cloneable).

Here's a simple test-case with JUnit:

@Test   
public void test()
{
    Stack intStack = new Stack();
    for(int i = 0; i < 100; i++)        
    {
        intStack.push(i);
    }

    Stack copiedStack = (Stack)intStack.clone();

    for(int i = 0; i < 100; i++)            
    {
        Assert.assertEquals(intStack.pop(), copiedStack.pop());
    }
}

Edit:

tmsimont: This creates a "unchecked or unsafe operations" warning for me. Any way to do this without generating this problem?

I at first responded that the warning would be unavoidable, but actually it is avoidable using (wildcard) -typing:

@Test
public void test()
{
    Stack intStack = new Stack();
    for(int i = 0; i < 100; i++)
    {
        intStack.push(i);
    }

    //No warning
    Stack copiedStack = (Stack)intStack.clone();

    for(int i = 0; i < 100; i++)
    {
        Integer value = (Integer)copiedStack.pop(); //Won't cause a warning, no matter to which type you cast (String, Float...), but will throw ClassCastException at runtime if the type is wrong
        Assert.assertEquals(intStack.pop(), value);
    }
}

Basically I'd say you're still doing an unchecked cast from ? (unknown type) to Integer, but there's no warning. Personally, I'd still prefer to cast directly into Stack and suppress the warning with @SuppressWarnings("unchecked").