stack.java

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package stack;

 import java.util.Arrays;

/**
 *
 * @author DELL
 * @param <T>
 */
public class Stack<T> implements stackInterface<T> {
    
    private T[] array;

    //WHAT DOES THIS DO, WHAT ARE GENERICS
    
    public Stack() {
        this.array = new T[0];
    }

    /**
     * @param t
     */
    
    //we should use  an array

    @Override
    public void push(T t) {
        
        //creates a temp array with 1+ length from the first
        T[] temp = new T[array.length+1];

        //loops through array to add the old values
        System.arraycopy(array, 0, temp, 0, array.length);
        
        array = temp;
        
        array[array.length-1] = t;
    }

    @Override
    public T pop(T t) {
        
        //if the array is empty return null
        if(array.length == 0){
            return null;
        }
        //value to be popped
        T poppedValue;
        poppedValue = array[array.length-1];
        //make it smaller by one
        T[] temp = new T[array.length-1];
        //add from index 0 to 1 less
        System.arraycopy(array, 0, temp, 0, array.length-1);
        //return that first value
        return poppedValue;
    }

    @Override
    public T peek(T t) {
        //this is just to see what value is at the top of the stack
        
        //if the array is empty return null
        if(array.length == 0){
            return null;
        }
        
        return array[array.length-1];
        
    }

    @Override
    public boolean empty() {
        //checks if the array is empty
        return array.length == 0;
    
    }
}
    

stackInterface.java

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package stack;

/**
 *
 * @author DELL
 * @param <T>
 */
public interface stackInterface <T> {
    //adds object to top of the stack, doesnt return anything
    void push(T t);

    //removes object from top of the stack, returns the removed value
    T pop(T t);

    //checks what object is on top of stack
    T peek(T t);

    //checks if stack is empty, returns boolean
    boolean empty();
}

@Sisekelo