Using string and logic operators in if statements

Question

I'm new to learning Java. I started about a week ago, and have spent around 10 hours a day learning, and I'm not sure if I'm behind where I "should be" (another concern I'm dealing with) I'm aware that my code is probably not the most efficient, but I have to start somewhere, and I've typed most of this out of memory from the cosmos of information I've read in the last week. Right now, I'm just trying to make games or apps to help solidify concepts of programming. To put what I've learned to use and make this information relevant.

my question is, essential, why are my "if" statements going directly to the "else"?

public class ClassSelect {

public static String className;

public static void pickPlayer() {

    Scanner scan = new Scanner(System.in);
    System.out.println("Pick your class." + "\n" + "[F]ighter" + "\n"
            + "[W]izard");
    String scanClass = scan.nextLine();

    if ((scanClass == "f") || (scanClass == "F")) {
        System.out.println("You picked the Fighter");
        String classNameF = "Fighter";
        className = classNameF;
        try {
            File file = new File("saveData.txt");
            BufferedWriter output = new BufferedWriter(new FileWriter(file));
            output.write(className);
            output.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    else if ((scanClass == "w") || (scanClass == "W")) {
        System.out.println("You picked the Wizard");
        String classNameW = "Wizard";
        className = classNameW;
        try {
            File file = new File("saveData.txt");
            BufferedWriter output = new BufferedWriter(new FileWriter(file));
            output.write(className);
            output.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    } else {
        System.out.println("You didn't choose either.");
    }
}

On this site the RPG tag refers to a programming language. Please read our tag info before using them. Thank you. — WarrenT, Aug 05 '13 at 13:54

score 3 · Accepted Answer · answered Aug 05 '13 at 08:34

3

For string comparison, you must use equals method of Object class. Your if statements will become like - if(scanClass.equals("f"))...

Remember, == compares reference and not the actual object.

answered Aug 05 '13 at 08:34

Ved

8,577
7
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1

Better yet if("f".equals(scanClass)){} – Sajal Dutta Aug 05 '13 at 08:48
To improve it further: if("f".equalsIgnoreCase(scanClass)... saves you the more bulkish way of two compares. – LastFreeNickname Aug 05 '13 at 08:55
Thank you, and everyone that answered. Sorry for such a noob question, but I honestly can't recall seeing "equals" in any of the online documents I've read, though I could be mistaken. – Surlistyc Aug 05 '13 at 09:03
@Surlistyc If you feel your question is answered properly, you can accept the answer by clicking on right mark under down arrow. – Ved Aug 05 '13 at 12:28
@SajalDutta Agreed.:) – Ved Aug 05 '13 at 12:29
@LastFreeNickname My suggestion was for avoiding NPE, not for "bukish way of two compares"..not sure what that means. – Sajal Dutta Aug 05 '13 at 12:34
@SajalDutta Exactly, that's why I gave your comment +1. It's an mistake made too often. My line was only to avoid if("f".equals... || "F".equals...). – LastFreeNickname Aug 05 '13 at 15:06

score 0 · Answer 2 · answered Aug 05 '13 at 08:39

0

Always compare Strings using equals.

== compares the references.

equals() on the other hand compares the values.

if ((scanClass.equals("f") || (scanClass.equals("F")))

answered Aug 05 '13 at 08:39

Ankur Lathi

7,636
5
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49

score 0 · Answer 3 · answered Aug 05 '13 at 08:45

0

You should be using scanClass.equalsIgnoreCase("f") in if statements because == operator compares references not values.

answered Aug 05 '13 at 08:45

Nils

806
1
9
24

score 0 · Answer 4 · answered Aug 05 '13 at 09:00

The operator, ==, tests to see if two object reference variables refer to the exact same instance of an object.

The method, .equals(), tests to see if the two objects being compared to each other are equivalent -- but they need not be the exact same instance of the same object. So

 if ((scanClass == "f") || (scanClass == "F"))

evaluates to false and control goes to the else block .

Using string and logic operators in if statements

4 Answers4