ArrayStack

package stackPractice;



/**
 *
 * @author acer
 */
public class ArrayStack implements Stack{
    int size;
    Object [] data;
    int top;

    public ArrayStack(){
    size=0;
    top=-1;
    data=new Object[7];

    }

    // The number of items on the stack
    public int size(){
        return top+1;
    }
// Returns true if the stack is empty
    public boolean isEmpty(){
        if(top==-1){
            return true;
        }else{
            return false;
        }
    }
// Pushes the new item on the stack, throwing the
// StackOverflowException if the stack is at maximum capacity. It
// does not throw an exception for an "unbounded" stack, which
// dynamically adjusts capacity as needed.
    public void push(Object e) throws StackOverflowException{
        if(top+1==data.length){
            throw new StackOverflowException();

        }

            top++;
            data[top]=e;
            size++;

    }
// Pops the item on the top of the stack, throwing the
// StackUnderflowException if the stack is empty.
    public Object pop() throws StackUnderflowException{
        if(top==-1){
            throw new StackUnderflowException();
        }

            Object val=data[top];
            data[top]=null;
            top--;
            size--;
            return val;

      }
// Peeks at the item on the top of the stack, throwing
// StackUnderflowException if the stack is empty.
    public Object peek() throws StackUnderflowException{
        if(top==-1){
            throw new StackUnderflowException();
        }
        return data[top];
    }
// Returns a textual representation of items on the stack, in the
// format "[ x y z ]", where x and z are items on top and bottom
// of the stack respectively.
    public String toString(){
        String str="[";
        for(int i=top;i>=0;i--){
            if(i==0){
                str+=data[i]+"]";
            }else{
            str+=data[i]+",";
            }
        }
        return str;
    }
// Returns an array with items on the stack, with the item on top
// of the stack in the first slot, and bottom in the last slot.
    public Object[] toArray(){
        Object [] arr=new Object[size()];
        int k=0;
        for(int i=top;i>=0;i--){
            arr[k]=data[i];
            k++;
        }
        return arr;
    }
// Searches for the given item on the stack, returning the
// offset from top of the stack if item is found, or -1 otherwise.
    public int search(Object e){
       int idx=-1;

        for(int i=0;i<size();i++){
            if(e.equals(data[i])){
               idx=i;
            }
        }
        return idx;
    }


}