Findbugs SIO_SUPERFLUOUS_INSTANCEOF

In my findbugs report I have a SIO_SUPERFLUOUS_INSTANCEOF correctness error in the following code section

/** Allow Comparison based on User-Labels */
public int compareTo(AbstractListItem o) {
    if ( !( o instanceof AbstractListItem ) ) {
        // Correctness - Unnecessary type check done using instanceof operator
        // : Method com.x.y.gui.topolog开发者_开发技巧y.TopologyListNode.compareTo (AbstractListItem) 
        // does an unnecessary type check using instanceof operator when it 
        // can be determined statically
    return -1;
}

What is the correct way to statically determine the type?

public int compareTo(AbstractListItem o) - o is an AbstractListItem, you don't need to check.

If you had public int compareTo(Object o) then your instanceof would be needed and not produce a warning.

In your code the type of object o is already statically determined as AbstractListItem, and therefore the instanceof is unnecessary. Findbugs reported it as a warning because it may be a sign of bug, e.g., what you wanted to check was a subtype of AbstractListItem, but you'd typed AbstractListItem by mistake.