我在尝试将堆栈实现为数组的过程中不断收到“找不到符号”错误

Question

So for an assignment I need to implement a Stack using an array. I have all of the code figured out, but for some reason whenever I try to use my char array, Java says it can't find it. Here is my stack class.

public class Stack
{
    private int top;

    public Stack ()
    {
        char []charArray = new char [50];
        top = -1;
    }

    public void push(char c)
    {
        top++;
        charArray[top] = c;
    }

    public void pop()
    {
        top--;
    }

    public char top()
    {
        return charArray[top];
    }

    public void makeNull()
    {
        top=-1;
    }

    public boolean isEmpty()
    {
        return (top==-1);
    }
}

Does anyone have any idea why I'm having these errors? It doesn't like the lines in push and top where I reference charArray.

Answer 1

The array variable charArray is declared as a local variable inside the constructor, and thus is not visible to the other methods.

You can declare it as a member field:

 private int top;
 private char[] charArray;

 public Stack ()
 {
    charArray = new char [50];
    top = -1;
 }