Editing Fragile base class (section)

==Java example==
The following trivial example is written in the [[Java programming language]] and shows how a seemingly safe modification of a base class can cause an inheriting subclass to malfunction by entering an [[infinite recursion]] which will result in a [[stack overflow]].
<syntaxhighlight lang="java">
class Super {
    private int counter = 0;

    void inc1() {
        counter++;
    }

    void inc2() {
        counter++;
    }
}

class Sub extends Super {
    @Override
    void inc2() {
        inc1();
    }
}
</syntaxhighlight>

Calling the dynamically bound method ''inc2()'' on an instance of ''Sub'' will correctly increase the field ''counter'' by one. If however the code of the superclass is changed in the following way:
<syntaxhighlight lang="java">
class Super {

    private int counter = 0;

    void inc1() {
        inc2();
    }

    void inc2() {
        counter++;
    }
}
</syntaxhighlight>

a call to the dynamically bound method ''inc2()'' on an instance of ''Sub'' will cause an infinite recursion between itself and the method ''inc1()'' of the super-class and eventually cause a stack overflow. This problem could have been avoided, by declaring the methods in the superclass as '''final''', which would make it impossible for a sub-class to override them. However, this is not always desirable or possible. Therefore, it is good practice for super-classes to avoid changing calls to dynamically-bound methods.