getBoolean(String str) and valueOf(String str) of Boolean class gives different output

Question

I am surprised to know that getBoolean() and valueOf() method returns different results for the same input string.

I have tried to pass the

Answer 1

class Boo1
{    
    public static void main(String[] args)
    {    
       System.setProperty("true","true");
       System.setProperty("false","true");

       boolean d=Boolean.getBoolean("true");

       System.out.println(d);   
   }
}

Answer 2

I too found this issue recently when using Boolean.getBoolean() . In addition if you want to have a null check you can use Boolean.parseBoolean which will return false in case of nulls

Answer 3

                                     The API-documentation is your friend.

• Boolean.getBoolean probably doesn't do what you think it does:

  Returns true if and only if the system property named by the argument exists and is equal to the string "true".

• Boolean.valueOf is probably what you're looking for:
  

  The Boolean returned represents the value true if the string argument is not null and is equal, ignoring case, to the string "true".

Answer 4

Boolean.getBoolean must be the worst placed method in java. One of the big WTF.

Why wasn't it placed in System or Properties or whatever?

So to answer your question - yes, it is a very confusing thing and you can just click on the method in your IDE to see the code or read the javadoc.

Here's the source code:

 public static boolean getBoolean(String name) {
        boolean result = false;
        try {
            result = toBoolean(System.getProperty(name));
        } catch (IllegalArgumentException e) {
        } catch (NullPointerException e) {
        }
        return result;
    }

Answer 5

The javadoc of getBoolean clearly state that it searches the System Properties. The value that you pass to it is the name of the system property, not a "true" or "false" string.

E.g., `var b = Boolean.getBoolean("some.property");