StackUsingArray.java

package stack;

public class StackUsingArray {
    private int[] data;
    private int top;
    public static final int DEFAULT_CAPACITY = 10;

    public StackUsingArray() throws Exception{
        this(DEFAULT_CAPACITY);

    }
    public StackUsingArray(int capacity) throws Exception {
        if (capacity<1){
            throw new Exception("Invalid capacity");
        }
        this.data = new int[capacity];
        this.top = -1;

    }

    public int size(){
        return this.top + 1;
    }

    public boolean isEmpty(){
                return this.size() == 0;
    }

    public void push(int value) throws Exception{
        if(this.size()==this.data.length){
            throw new Exception("stack is full");
        }

        this.top++;
        this.data[this.top] = value;
    }

    public  int pop() throws Exception{
        if(this.size() == 0 ){
            throw new Exception("the stack is already empty");
        }
        int rv = this.data[this.top];
        this.data[this.top] = 0;
        this.top--;
        return rv;
    }


    public  int top() throws Exception{
        if(this.size() == 0 ){
            throw new Exception("the stack is already empty");
        }
        int rv = this.data[this.top];
        
        return rv;
    }
    
    public void display(){
        for (int i = this.top; i >=0 ; i--){
            System.out.println(this.data[i]+",");
            
        }

        System.out.println();

    }



}