java-me: Convert String to boolean

Question

I'm developing for BlackBerry and I got stuck with this stupid problem:

I need to convert string values "1" and "0" to true and false, respectively. Nevertheless, Blackberry JDK is based in Java 1.3, so I can't use Boolean.parseBoolean, Boolean.valueOf or Boolean.getValue.

Obviously I can do something like:

if (str.equals("1")) return true;
else if (str.equals("0")) return false;

But this looks very ugly and maybe these string values could change to "true" and "false" later. So, Is there another way to convert between these types (String -> boolean, Java 1.3)?

UPDATED: all the answers of this question was very helpfully but I needed to mark one, so I selected Ishtar's answer.

Even so, my fix was a combination of multiple answers.

This question leads me to the DailyWTF article. I am not insulting you just merely suggesting that Boolean values changing should be a very very rare occurrence read http://thedailywtf.com/Articles/What_Is_Truth_0x3f_.aspx keep it simple even if you do hard code the "1" or "true" in the function it is ok. Somethings are just certainties else they would never have made it into the core language. — drubin, Mar 25 '11 at 14:02

score 14 · Accepted Answer · answered Mar 25 '11 at 16:48

public static boolean stringToBool(String s) {
  if (s.equals("1"))
    return true;
  if (s.equals("0"))
    return false;
  throw new IllegalArgumentException(s+" is not a bool. Only 1 and 0 are.");
}

If you later change it to "true/false", you won't accidentally order 28,000 tons of coal. Calling with the wrong parameter will throw an exception, instead of guessing and returning false. In my opinion "pancake" is not false.

score 9 · Answer 2 · answered Mar 25 '11 at 05:24

If you don't have Boolean.valueOf(String s) ... yeah, that's pretty much it. I'd define your own static method like:

public static boolean booleanFromString(String s)
{
    return s.equals("1");
}

That would solve your "May change to true or false later" problem as you could add/change that in the method and not have to change anything else in your code.

Prince John Wesley · Answer 3 · 2011-03-25T05:52:16.253

2

maybe these string values could change to "true" and "false" later

Don't hard code your parameter.

So define your own method like this.

public static final String TRUE = "true"; //"1"

public static boolean strToBool(String s) {
    // don't hard code your parameter.
    return str.equalsIgnoreCase(TRUE);
}

edited Mar 25 '11 at 05:52

answered Mar 25 '11 at 05:32

Prince John Wesley

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Actually.. this is one case where I *would* hard-code my parameter as the definition of a "true" string is a (or a set of) very particular value(s). +1 though. – Mar 25 '11 at 05:45
@pst: you are right. but the OP's case is different. see --> `string values could change ` – Prince John Wesley Mar 25 '11 at 05:49
@John Then I'd change them in the method ;-) – Mar 25 '11 at 05:54
@pst: again you are right. so the answer is to encapsulate it into the method. – Prince John Wesley Mar 25 '11 at 05:56
@Brian: change the method body. or split the method into two. anyhow, document it. – Prince John Wesley Mar 25 '11 at 05:59

score 2 · Answer 4 · answered Mar 25 '11 at 06:27

Java's Boolean object (if I remember correctly) has already 2 constants:

Boolean.TRUE
Boolean.FALSE

you can use Boolean.booleanValue() to return it's corresponding boolean value.

You can create your own valueOf(String s) method to return a boolean and/or Boolean like so:

public static boolean toBoolean(String s) {
    return ((s != null) && s.equalsIgnoreCase("true"));
}

public static Boolean valueOf(String s) {
    return (toBoolean(s)? Boolean.TRUE : Boolean.FALSE);
}

score 2 · Answer 5 · answered Mar 25 '11 at 14:01

2

you should check null and whitespace chars. remove them and check value.

return (str!=null && str.trim().equals("1"));

answered Mar 25 '11 at 14:01

y0rk

396
1
8

score 0 · Answer 6 · edited May 23 '17 at 10:27

public static boolean stringToBool(String s) {
        s = s.toLowerCase();
        Set<String> trueSet = new HashSet<String>(Arrays.asList("1", "true", "yes"));
        Set<String> falseSet = new HashSet<String>(Arrays.asList("0", "false", "no"));

        if (trueSet.contains(s))
            return true;
        if (falseSet.contains(s))
            return false;

        throw new IllegalArgumentException(s + " is not a boolean.");
}

Enhance Ishfar answer.

java-me: Convert String to boolean

6 Answers6