Java returning a string from a stack

Question

I am supposed to reverse the individual words in a sentence using a helper method that takes a string as a parameter and returns a string. The stack is supposed to be in the helper method. So my program works in that it reverses the words correctly. But reverse isnt actually getting returned, i think its just printing the stack. Can anyone help me return and print the string variable 'reverse'.

import java.util.Scanner;
import java.util.Stack;

public class ReverseStack 
{
    public static void main(String[] args)
    {
        String sentence;

        System.out.print("Enter a sentence: ");
        Scanner scan = new Scanner(System.in);

        sentence = scan.nextLine();

        System.out.println("Reversed:" + PrintStack(sentence));
    }

    private static String PrintStack(String sentence)
    {
        String reverse = "";
        String next = "";

        Stack<String> stack= new Stack<String>();

        String words[] = sentence.split(" ");

        for(int j = 1; j<words.length +1; j++)
        {
            String newWord = words[words.length - j]; // Single word

             for(int i = 0; i < newWord.length(); i++)
            {
                    next = newWord.substring(i,i+1);
                    stack.push(next);
            }
             stack.push(" ");
        }
        while(!stack.isEmpty())
        {
            reverse += stack.pop();
        }
        return reverse;
    }   
}

Your program is returning and printing the string variable 'reverse'. — Simon Soriano
– Simon Soriano, Commented Feb 13, 2014 at 14:58
@Simon But isnt it printing out the stack not the reverse string? Its printing PrintStack(sentence) not reverse — user3071909
– user3071909, Commented Feb 13, 2014 at 15:35
@user3071909 Well, we can say that you are printing both: 'PrintStack(sentence)' since you are calling it inside the Sysout and 'reverse' since it is the return value of 'PrintStack' method. Then, I don't understand what seems wrong to you. — Simon Soriano
– Simon Soriano, Commented Feb 13, 2014 at 15:42
@Simon oohhh so it is returning and printing reverse. I was just confused. Is the use of the stack correct, in terms of reversing the words? — user3071909
– user3071909, Commented Feb 13, 2014 at 15:48

Peter Lawrey · Accepted Answer · 2014-02-13 14:56:57Z

1

You are reversing twice and ending up with the same order. Your Stack gives reverse order, but you are adding the words in reverse order, so the order is unchanged.

If you used a debugger it should be obvious to you what the issues is.

BTW You can make the code much shorter.

private static String printStack(String sentence) {
    Stack<String> stack= new Stack<String>();
    for(String word: sentence.split(" ")
        stack.push(word);
    String line = stack.pop();
    while(!stack.isEmpty())
        line += " " + stack.pop();
    return line;
}

answered Feb 13, 2014 at 14:56

Peter Lawrey

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