Run this test case with jdk7-b100:

import java.text.*;

public class Test {
    public static void main(String[] args) {
        Collator c = Collator.getInstance();
        c.compare("foo", "bar");
        c.compare("foo", null);
    }
}

and it fails with this:

Exception in thread "main" java.lang.IllegalArgumentException
        at sun.text.normalizer.ReplaceableUCharacterIterator.<init>(ReplaceableUCharacterIterator.java:60)
        at sun.text.normalizer.UCharacterIterator.getInstance(UCharacterIterator.java:84)
        at sun.text.normalizer.NormalizerBase.setText(NormalizerBase.java:1002)
        at java.text.CollationElementIterator.setText(CollationElementIterator.java:497)
        at java.text.RuleBasedCollator.compare(RuleBasedCollator.java:372)
        at Test.main(Test2.java:8)

It shoud of course fail with NullPointerException (not IAE).