Comparing a Scanner string to a manually typed string

[Valgarv]

import java.util.Scanner;

public class test {

    public static void main(String[] args) {
        
        String testOne = "foo";
        String testTwo = "foo";
             
        Scanner scan = new Scanner(System.in);
        System.out.print("Insert \"foo\" as a value for busted: ");
        String busted = scan.next();
        if (testOne == busted)
            System.out.println("scanned string comparison is working");
        else if (testOne == testTwo)
            System.out.println("predefined string comparison is working");
        else
            System.out.println("String comparison is completely busted");      
    }
} 

When this is run and I enter "foo" for scanner the first if statement is false. Why does this happen?

[Phaelax]

The "==" operator when used with strings, compares the memory location of the two strings, not the actual text. use the String's equal() method.

if (testOne.equals(busted))

[cjard]

if there is the possibility that one string will be null, either test for that null first, or swap the .equals clauses over:

//test for null
if(userInput!=null && userInput.equals("quit"){

//rearrange
if("quit".equals(userInput))


in the first case, if userInput is null the first condition is FALSE. false, ANDed with anything will always be false, so java gives up without testing the second part. order of evaluation is always left to right

in the second case, "quit" is a string literal and will never be null. you can think of it like this if it helps:

new String("quit").equals(userinput)

if null is fed into .equals() then the result will always be false, as the only thing it could be true with, is another null (but that would cause an exception):

String s = null;
s.equals(null) //bang! nullpointer exception because s is null (cant call equals method)

so.. er.. yeah.. 2 tips for avoiding problems

[Valgarv]

Appreciate the help. Thanks guys. Java is a whole new world for me.