CODEWITHSUNDEEP
javaloopsif-statementboolean
user3066571
user3066571

Reputation: 1471

Boolean always outputs true

I have a class to test a palindrome. In my loop, it compares each letter to see if they match, if they don't, it's supposed to make the boolean variable as false, or vice versa. Now I've tested it a ton, and I can see that if I correctly put in a palindrome, it actually goes to the correct if statement which makes the variable true. If it comes across a pair of letters which don't match, it's supposed to declare the boolean variable as false and break from the loop, which it actually does properly. But no matter what, the boolean variable is always true when I try to use it to determine what response comes back, and I have no idea why.

 is a palindrome!  Hooray!

is ALWAYS the output, even if the loop goes to the false boolean and breaks, and it baffles me.

public class Palindrome
{
public static void main(String[] args) 
{
    //is it true?
    boolean truth;
    //create stack and queue
    Stack s = new Stack();
    Queue q = new LinkedList();
    //scanner
    Scanner input = new Scanner(System.in);
    //get string
    System.out.println("Enter a palindrome, or don't, I'll know:");
    String palin = input.nextLine();
    //remove whitespace
    palin = palin.replaceAll("\\s+","");
    System.out.println(palin);
    //remove puncuation
    palin = palin.replaceAll("\\p{P}", "");
    System.out.println(palin);
    //set lowercase
    palin = palin.toLowerCase();
    System.out.println(palin);

    //feed string to stack and queue
    for(int i = 0; i < palin.length(); i++)
    {
        s.push(palin.charAt(i));
        q.add(palin.charAt(i));
    }
    System.out.println(s);
    System.out.println(q);
    while(!s.isEmpty() && !q.isEmpty())
    {
        Object sTemp = s.pop();
        Object qTemp = q.poll();
        String sString = sTemp.toString();
        String qString = qTemp.toString();
        System.out.println(sString + qString);
        System.out.println("looptest");
        if(sString.equals(qString))
        {
            truth = true;
        }
        else
        {
            truth = false;
            break;
        }
    }
    if(truth = true)
    {
        System.out.println(palin + " is a palindrome!  Hooray!");
    }
    else
    {
        System.out.println(palin + " is no palindrome! You lied!");
    }
}
}

Upvotes: 0

Views: 274

Answers (2)

bumbumpaw
bumbumpaw

Reputation: 2530

basic ,but most programmer(beginner) tend to typo-error or just dont know the difference of = and == or meet them officially, so here it goes

= is assignment operator and == test for equality or conditional operator

so in your line

 if(truth = true)
    {
       ...
    }

you are assigning your variable truth to have true as value

Gotta use the == so value of your boolean wont change.

if(truth == true)
    {
      ...
    }

or

if(truth.equals(true))
    {
       ...
    }

Upvotes: -1

rgettman
rgettman

Reputation: 178253

With this line

if(truth = true)

You are assigning true to truth with =, when you probably meant == to compare. It's already a boolean, so just have it as the condition.

if (truth)

Upvotes: 7

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