Question

In Java, I use a class in which some fields can be null. For example:

class Foo {     String bar;     //.... } 

I want to write a BarComparator for this class,

    private static class BarComparator             implements Comparator<Foo> {         public int compare( final Foo o1, final Foo o2 )         {             // Implementation goes here         }     } 

Is there a standard way to deal with the fact that any of o1, o2, o1.bar, o2.bar can be null, without writing lots of nested if…else?

Cheers!

Answer 1

I guess you could wrap the call to the field compareTo method with a small static method to sort nulls high or low:

static <T extends Comparable<T>> int cp(T a, T b) {      return          a==null ?          (b==null ? 0 : Integer.MIN_VALUE) :          (b==null ? Integer.MAX_VALUE : a.compareTo(b)); } 

Simple usage (multiple fields is as you would normally):

public int compare( final Foo o1, final Foo o2 ) {     return cp(o1.field, o2.field); }