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copied!<blockquote> <p><em>what I want to know is why java forbids static fields/methods inside inner classes</em></p> </blockquote> <p>Because those inner classes are "instance" inner classes. That is, they are like an instance attribute of the enclosing object. </p> <p>Since they're "instance" classes, it doesn't make any sense to allow <code>static</code> features, for <code>static</code> is meant to work without an instance in the first place.</p> <p>It's like you try to create a static/instance attribute at the same time. </p> <p>Take the following example: </p> <pre><code>class Employee { public String name; } </code></pre> <p>If you create two instances of employee: </p> <pre><code>Employee a = new Employee(); a.name = "Oscar"; Employee b = new Employee(); b.name = "jcyang"; </code></pre> <p>It is clear why each one has its own value for the property <code>name</code>, right? </p> <p>The same happens with the inner class; each inner class instance is independent of the other inner class instance.</p> <p>So if you attempt to create a <code>counter</code> class attribute, there is no way to share that value across two different instances. </p> <pre><code>class Employee { public String name; class InnerData { static count; // ??? count of which ? a or b? } } </code></pre> <p>When you create the instance <code>a</code> and <code>b</code> in the example above, what would be a correct value for the static variable <code>count</code>? It is not possible to determine it, because the existence of the <code>InnerData</code> class depends completely on each of the enclosing objects. </p> <p>That's why, when the class is declared as <code>static</code>, it doesn't need anymore a living instance, to live itself. Now that there is no dependency, you may freely declare a static attribute.</p> <p>I think this sounds reiterative but if you think about the differences between instance vs. class attributes, it will make sense. </p>

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