Why is my program not recognizing the comparison between two strings in an if statement?

Question

Here is my code (question listed below): import java.util.Scanner;

public class ExampleCode {

/**
 * B. Stephens
 */
public static void main(String[] args) {

    Scanner input = new Scanner (System.in);

    String secretPhrase = "show me the money";
    boolean notDone = true;

    while (notDone = true){
        System.out.print("Guess the puzzle: ");
        String puzzleGuess = input.nextLine();
        if (puzzleGuess == secretPhrase) {
            System.out.println("Congratulations! You guessed the puzzle!");
            notDone = false;
        }
    }

} // end main

For some reason, the program isn't recognizing when my input (puzzleGuess) is the same as secretPhrase. It seems like there is no reason the correct input shouldn't end the program. Thanks for any help!

Don't compare content of Strings using `==`. Use `equals()` instead. — Alexis C., Dec 15 '13 at 23:02

score 1 · Answer 1 · answered Dec 15 '13 at 23:04

1

Use .equals() instead of == so, your if-statement should be like this: if (puzzleGuess.equals(secretPhrase))

as the String is considered to be an object, and any objects comparison must be performed using .equals(Object o).

Hope my answer did help :)

answered Dec 15 '13 at 23:04

Khaled Hassan

156
1
8

`and any objects comparison must be performed using .equals(Object o).` Phrased like that, what you're saying is false. – Sotirios Delimanolis Dec 15 '13 at 23:11
Hi Sotirios Delimanolis :) can you please tell me why is it false? I always compare objects (strings or from any other class) using .equals() – Khaled Hassan Dec 15 '13 at 23:14
`must` is the issue. It always depends on what you are trying to do. – Sotirios Delimanolis Dec 15 '13 at 23:16
okay, got your point :) – Khaled Hassan Dec 15 '13 at 23:19

score 0 · Answer 2 · answered Dec 15 '13 at 23:03

because you need to use the .equals method

if (puzzleGuess.equals(secretPhrase)) {
    System.out.println("Congratulations! You guessed the puzzle!");
    notDone = false;
}

Java Strings are interned so == can sometimes work.

public class InternedDemo {

    public static void main(String[] args) {
        String s1 = "hello world";
        String s2 = "hello world";
        String s3 = new String("hello world");

        System.out.println(s1 == s2); // true
        System.out.println(s1 == s3); // false
        System.out.println(s2 == s3); // false

       System.out.println(s1.equals(s3)); // true
       System.out.println(s2.equals(s3)); // true
   }
}

String *Literals* are interned. Dynamically created Strings are only interned if done so explicitly. — Sinkingpoint, Dec 15 '13 at 23:06

score 0 · Answer 3 · answered Dec 15 '13 at 23:04

0

Don't compare strings using ==. Use secretPhrase.equals(puzzleGuess). == is just checking if both strings are the same object.

answered Dec 15 '13 at 23:04

splrs

2,424
2
19
29

Hammad · Answer 4 · 2013-12-15T23:30:57.273

0

Use .equals() to compare to string

public static void main(String[] args) {

Scanner input = new Scanner (System.in);

String secretPhrase = "show me the money";
boolean notDone = true;

while (notDone){
    System.out.print("Guess the puzzle: ");
    String puzzleGuess = input.nextLine();
    if (puzzleGuess.equals(secretPhrase)) {
        System.out.println("Congratulations! You guessed the puzzle!");
    secretPhrase=null;
        notDone = false;
    }
   }
}

edited Dec 15 '13 at 23:30

answered Dec 15 '13 at 23:05

Hammad

101
1
10

1

`while (notDone = true)` ? – ChiefTwoPencils Dec 15 '13 at 23:29

score 0 · Answer 5 · answered Dec 15 '13 at 23:10

== cannot be used to compare Strings. For non-primitives, == determines whether they are the same object. To see whether the two strings have the same value, instead use .equals():

String str1 = new String("foo");
String str2 = str1;
String str3 = new String("foo");
String str4 = new String("bar");
System.out.println(str3 == str3); //true
System.out.println(str1 == str2); //true
System.out.println(str1 == str3); //FALSE!
System.out.println(str1.equals(str3)); //true!
System.out.println(str1 == str4); //false
System.out.println(str1.equals(str4)); //false

== can be used to compare Strings, or any other Object for that matter. It is reference equality vs actual equality. — Sinkingpoint, Dec 15 '13 at 23:20

Why is my program not recognizing the comparison between two strings in an if statement?

5 Answers5