Implementing `Stack` from scratch

Question

I'd like to implement Stack from scratch and encountered a problem. I feel like I'm writing the parameters for push method wrong such as:

public void push(<T> foo){
    myList.add(foo);
}

How else can I write the parameter when I'm not sure what type the foo is going to be?

package Stack;
import java.util.*;

public class Stack<T> {

    private List<T> myList;

    public Stack(){
        myList = null;
    }

    public boolean empty(){
        return (myList == null);
    }

    public void push(<T> foo){
        myList.add(foo);
    }
}

public void push(T foo){ myList.add(foo); } Remove the angular brackets from around `T`. — Chthonic Project, Jul 26 '15 at 19:40
"I feel like I'm writing the parameters for push method wrong" why do you think so? Do you get any error (except obvious NPE since `myList` is `null`)? — Pshemo, Jul 26 '15 at 19:42
@John http://stackoverflow.com/questions/6607550/what-does-angle-brackets-mean-in-java check this.. Might help! — user007, Jul 26 '15 at 19:44
@John: http://stackoverflow.com/questions/6607550/what-does-angle-brackets-mean-in-java — Chthonic Project, Jul 26 '15 at 19:44

score 4 · Accepted Answer · answered Jul 26 '15 at 19:41

4

public void push(T foo) {
    myList.add(foo);
}

You can read more on generics here.

answered Jul 26 '15 at 19:41

Emile Pels

3,837
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score 0 · Answer 2 · answered Jul 26 '15 at 19:40

0

The correct syntax is :

public void push(T foo) {
    myList.add(foo);
}

answered Jul 26 '15 at 19:40

ttzn

2,543
22
26

score 0 · Answer 3 · answered Jul 26 '15 at 19:41

0

It just needs to be

public void push(T foo){
    myList.add(foo);
}

answered Jul 26 '15 at 19:41

user007

2,156
2
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35

score -5 · Answer 4 · answered Jul 26 '15 at 19:42

-5

Type cast foo to Object type

public void push(Object foo){
    myList.add(foo);
}

answered Jul 26 '15 at 19:42

katwekibs

1,342
14
17

4

Terrible solution. He's using generics. Making push take `Object` just disables the type safety he can get from the generic solution. – Erick G. Hagstrom Jul 26 '15 at 19:42

Implementing `Stack` from scratch

4 Answers4