java.lang.NullPointerException with boolean

Question

I wrote a realy simple code based on another question and here it is:

It throws me an error

java.lang.NullPointerException line 5 and 17

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Answer 1

Your code compares a java.lang.Boolean instance with a primitive boolean, which means unboxing the java.lang.Boolean. Since null can't be unboxed, a NullPointerException is thrown.

You could work around this by using the built in constants Boolean.TRUE and Boolean.FALSE:

public static String bool(Boolean param) {
    if (Boolean.TRUE.equals(param)) {
        return "a";
    } else if (Boolean.FALSE.equals(param)) {
        return "b";
    }
    return "c";
}