Automated unit testing for maintaining object method contracts in Java?

When developing Java applications, I often rewrite object methods (usually equals and hashcode) I want some ways to systematically check whether I comply with the contract of object method in each course For example, I want to test to prove that hash codes are equal for equal objects I use JUnit testing framework, so it's better for me to want some JUnit solutions. I can automatically generate these tests, or some test cases, access all my courses and ensure that the contract is maintained

I use JDK6 and JUnit 4.4

Solution

    public static void checkObjectIdentity(Object a1,Object a2,Object b1) {

    public static void checkObjectIdentity(Object a1,Object a2,Object b1) {
        assertEquals(a1,a2);
        assertEquals(a2,a1);
        assertNotSame(a1,a2);
        assertEquals(a1.hashCode(),a2.hashCode());
        assertFalse(a1.equals(b1));
        assertFalse(a2.equals(b1));
        assertFalse(b1.equals(a1));
        assertFalse(b1.equals(a2));
    }

Usage:

        checkObjectIdentity(new Integer(3),new Integer(3),new Integer(4));

I can't think of anything better When you find an error, add a new call to checkobjectidentity