Pankaj Kumar's Weblog

How hard is test for equality in Java -- the answer will surprise you

A post at THE DAILY WTF includes a function with a compound if statement consisting of eight lines of code to set a flag when the Boolean argument is not equal to a Boolean member, suggesting that the code is correct but overly complex and verbose.

/**
    Set the value of the isRecordLocked attribute.
    @param newValue is the new isRecordLocked value.
*/
public void setIsRecordLocked(Boolean newValue) {
    // Update state if required.
    if (isRecordLocked != null) {
        if (newValue == null || !isRecordLocked.equals(newValue)) {
            context.setDirty(true);
        }
    }
    else if (newValue != null) {
        context.setDirty(true);
    }
    // Change the value.
    isRecordLocked = newValue;
}

The post also includes a suggestion that the compound if statement can be replaced entirely by a much more understandable one-liner, but doesn't really include the one-liner (perhaps obvious to the submitter).

I struggled for few minutes to figure out the obvious one liner, but couldn't come up with anything signficantly better. The problem is that a simple (A != B) doesn't work for Java Objects (and Boolean is an Object), for either A or B could be null and invoking equals method on null would result in a NullPointerException.

I clicked to see the comments, hoping to find the elusive one-liner in the copious comments (137, when I checked). No luck there. Though some people pointed out that there was nothing wrong with the code, most attempts to better the code resulted in buggy code.