Example

public static void main( String[] args ) {
Object o;
Object o2;
if (o==null && o.equals(o2)) {
o.toString();
}
}

Solution
    In the above example, a null pointer exception may occur when the method o.equals(o2) and o.toString() are executed.
    Reconsider the conditions in the if/else statement to ensure that a null-pointer exception will not be generated.

    Note: This rule also flags cases where an object, known to be null, is passed as a parameter.
    As the behaviour of the receiving method is not always predictable, this practice is discouraged.