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    <p>Solution for my concrete example of mixed-type equals() with default value constraints instead of ignoring the subclass value fields. Instead of Angelika Langer's solution (see <a href="http://www.angelikalanger.com/Articles/JavaSolutions/SecretsOfEquals/Equals-2.html" rel="nofollow">http://www.angelikalanger.com/Articles/JavaSolutions/SecretsOfEquals/Equals-2.html</a>) with private methods _compareFields() and a protected method _navigateClassHierarchy() that has to be copied into each subclass, only a protected method compareOwnFields() is used, which has to be overridden correctly in each subclass. </p> <pre><code>class SuperClass { // ... @Override public final boolean equals(final Object other) { if (other == this) { return true; } if (!(other instanceof SuperClass)) { return false; } final SuperClass otherSuperClass = (SuperClass) other; return compareOwnFields(otherSuperClass, false) &amp;&amp; otherSuperClass.compareOwnFields(this, true); } protected boolean compareOwnFields(final SuperClass other, final boolean firstTraversal) { if (!firstTraversal) { return true; } if (field1 != other.getField1()) { return false; } // compare other fields similarly ... return true; } } class SubClass { // ... @Override protected boolean compareOwnFields(final SuperClass other, final boolean firstTraversal) { if (other instanceof SubClass &amp;&amp; !firstTraversal) { return true; if (other instanceof SubClass) { if (field1 != ((SubClass) other).getField1()) { return false; } // compare other fields similarly ... return super.compareOwnFields(other, firstTraversal); } else { if (field1 != DEFAULT_FIELD1) { return false; } // check other fields for default values similarly .. return super.compareOwnFields(other, firstTraversal); } } } </code></pre> <p>But this does not answer my question in general, it's rather a redesign that avoids the problem. So further answers on how to solve the problem with the Java language features are very welcome!</p>
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    1. POIn Java: Code reuse possible for a chain of method calls up an inheritance hierarchy?
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    1. COJust a question: why are you comparing the fields twice - I mean it's like 'this.equals(other) && other.equals(this)`? Note that the contract for `equals()` states that if `this.getClass() != other.getClass()` the objects are not equal. Thus you could do something like `if( super.compareOwnFields((SuperClass)other) ) { compareOwnFields((SubClass)other); }`
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    2. COIf you are interested in equals(), I strongly recommend reading Angelikas articles about it. Just in short: this.getClass() != other.getClass() is not part of equal's contract. Many do it, but it is not conform to Liskov's substitution principle (see e.g. Effective Java item 8). To allow mixed-type equality, you do not have that constraint. I am calling o1.compareOwnFields(o2) and o2.compareOwnFields(o1) to cover the complete class hierarchy: E.g. SuperClass>SubA1>SubA2, SuperClass>SubB1>SubB2, o1 instanceof SubA2, o2 instanceof SubB2. By doing both calls, I compare all relevant fields.
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