将数组从构造函数传递给方法？

Question

When I try to run it I get this: Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0 I want to initialize the array in the constructor SimpleIntegerStack and use it later on in the methods that follow...

package datastructures.simple_integer_stack;

public class SimpleIntegerStack {
int maxSize;
private int stack[]=new int[maxSize];

public SimpleIntegerStack(int maxSize) {

    int stack[]= new int [maxSize];
}

public void push(int element) {
    int i=-1;
    boolean stop = false;

    do{
        if(stack[i]==0){
            stack[i]=element;
            stop=true;
        }
        i++;

    }while(stop=false && i<stack.length);

}

public void pop() {
    int i=0;

    while(stack[i]!=0 && i<stack.length){
        i++;
    }
    if(i!=0)
        stack[i] = 0;
}

public int top() {
    int stacktop=-1;
    int i=0;
    boolean empty = true;
    while(stack[i]!=0 && i<stack.length-1){
        i++;
        empty=false;
    }
    if(i==stack.length-1){
        if (stack[i+1]==0){
            empty=true;
        }
        else stacktop=stack[i+1];
    }
    if(empty=false)
        stacktop=stack[i-1];
    return stacktop;
}

}

Answer 1

Remove "int" from the code below:

public SimpleIntegerStack(int maxSize) {

    // dont do this:  int stack[]= new int [maxSize];
    stack = new int[maxSize];  
}

What you have done is to declare a local variable, stack in the constructor. This variable happens to have the same name as the instance variable. When the constructor function completes, the local variable goes out of scope.

Thus the instance variable, stack is not affected by calls to the constructor.