TernaryNpe.java

public class TernaryNpe {

    public static void main(String args[]) {
        final String a = "a";
        final String aa = "aa";

        final String b = null;
        final String bb = ""; 

        /* Test Case 1 */

        //OK
        boolean result = b == null ^ bb == null ?
            false : bb == null ? true : b.equals(bb);

        //NPE
        result =
            a.equals(aa)
                && b == null ^ bb == null ?
                false : bb == null ? true : b.equals(bb);


        /* Test case 2 */
        //OK
        result = (b == null ^ bb == null) ?
            false : (bb == null ? true : b.equals(bb));

        //NPE
        result =
            a.equals(aa)
            && (b == null ^ bb == null) ?
            false : (bb == null ? true : b.equals(bb));


        /* Test case 3 */
        //OK
        result = ((b == null ^ bb == null) ?
            false : (bb == null ? true : b.equals(bb)));

        //NPE
        result =
            (a.equals(aa)
                && (b == null ^ bb == null) ?
                false : (bb == null ? true : b.equals(bb)));

            System.out.println("RESULT=" + result);
    }   
}

Correct implementation is:

result =
            a.equals(aa)
            && (b == null ^ bb == null) ?
            false : (bb == null || b == null ? true : b.equals(bb));

or for Java 7:

result = 
            a.equals(aa)
            && Objects.equals(b, bb)