What is wrong with my code? [duplicate]

Question

When I run the following code:

class MyStack<T>
{
    private T[] stack;
    ... private T top;
    private static final int size=50;

    public MyStack()
    {
      stack = new int[size];
      top = 0;
    } 
}

I get this error

MyStack.java:18: generic array creation

stack = new T[size];
...
1 error

What should the proper code be, so I dont get this error

Community · Accepted Answer · 2017-05-23 11:55:25Z

6

You cannot instantiate a parameterized type in Java. and thus also not create arrays of it. Replace T[] by Object[] and create it as new Object[] and use casts against T in the methods whenever necessary.

Only if Java had Reified generics, it would be possible.

edited May 23, 2017 at 11:55

CommunityBot

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answered Apr 3, 2011 at 0:53

BalusC

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3 Comments

BalusC Over a year ago

I'd start to take a look in source code of java.util.Stack.

Paŭlo Ebermann Over a year ago

Nah, better look at ArrayList. The Stack class is only a subclass of Vector, so we don't even see the array there.

BalusC Over a year ago

@Paulo: ArrayList isn't a stack. An ArrayDeque would be better, but that's pretty complicated for a student. Also if OP knows basic Java, he should understand what class Stack extends Vector means and in any IDE you should be able to (Ctrl)click just Vector to see its source code.

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