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up vote 3 down vote favorite

Please review the code

package com.gmail.practice;

import java.util.Arrays;

public class StacksForTwo {

    int size;
    int[] stack;
    int top1;
    int top2;

    public StacksForTwo(int arraysize)
    {
        size = arraysize;
        stack = new int[size];
        top1 = -1;
        top2 = size;        
    }

    public void push1(int x)
    {
        if(top1 < top2-1)
        {
        top1++;
        stack[top1] = x;        
        }else{
            System.out.println("stackoverflow");
        }
    }

    public void push2(int y)
    {
        if(top1 < top2-1)
        {
            top2--;
            stack[top2] = y;
        }else{
            System.out.println("stack overflow");
        }
    }

    public void pop1()
    {
        if(top1 >= 0)
        {
            top1--;
            System.out.println("The popped out number is"+" "+stack[top1+1]);
        }else{
            System.out.println("stack underflow");
        }
    }

    public void pop2()
    {
        if(top2 < size)
        {
            top2++;
            System.out.println("The popped out number is"+" "+stack[top2+1]);
        }else{
            System.out.println("stack underflow");
        }
    }

    public void display()
    {
        System.out.println(Arrays.toString(stack));
    }

    public static void main(String[] args)
    {
        StacksForTwo sft = new StacksForTwo(10);
        sft.push1(4);
        sft.push1(5);
        sft.push1(3);
        sft.push1(2);
        sft.push2(6);
        sft.push2(4);
        sft.display();
        sft.push2(8);
        sft.push1(2);
        sft.push2(6);
        sft.push2(4);
        sft.push2(8);
        sft.display();
    }
}
share|improve this question
    
Could you please elaborate. Depending on your inputs i will try more things. –  dataEnthusiast yesterday

2 Answers 2

up vote 6 down vote

This code is a WOM implementation of a stack - Write Only Memory. Normally it's done as a joke. The only way to get the data out of the stack is to parse the standard output waiting for println statements with the values in them.

I can understand that your code is here for you to watch the process happening, but beyond that there's not much real functionality in here. I encourage you to use proper code where the pop() methods actually return their result, and the calling code is the code that prints the output. Alternatively, I strongly recommend you use the IDE's debugger interface to step through your code so you can watch things happen that way.

Having said all that, here are some general comments:

  1. your instance variables are not private, and should be.
  2. the size and stack variables should also be final
  3. instead of having a display() method, just override the toString()
  4. push1, and pop1 et all should probably be renamed to pushLeft and pushRight, or really anythong other than 1 and 2. You used the variables x and y so why not pushX and pushY?
share|improve this answer
    
Fields are default scope and can be accessed from classes in same package, anyway its pretty WOM. If he follow your suggestions its perfectly WOM. –  Peter Rader 20 hours ago
    
thanks for the inputs i will redo the code. –  dataEnthusiast 18 hours ago
up vote 4 down vote

I would go for

interface Stack {
    boolean isEmpty();
    int pop();
    void push(int x);
}

And then make a class providing two Stacks.

Also create a counter to detect when both stacks are full. This can be done with an AtomicInteger (thread-safeness) counting the free array slots.

public class StackPair {
    public final Stack firstStack = new Stack { ... };
    public final Stack secondStack = new Stack { ... };
    public StackPair(int capacity) { ... }
share|improve this answer

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