What is wrong with an inner class that doesn't use an outer class in Java?

Question

I use static analyzer in Eclipse to examine my code. One class, foo, has an inner class, bar. I get the following error:

JAVA0043 Inner class 'bar' does not use outer class 'foo'

Why is this a mistake? As long as the outer class uses the inner class, is it not enough that this information is hidden useful and correct?

The inner class is not static.

Answer 1

If the inner class can only be used by the outer class, but the inner class does not need a reference to the outer class, then you can do it private static.

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Answer 2

Enerjy Error:

// Incorrect
class Log {
  // Position never uses the enclosing Log instance,
  // so it should be static
  class Position {
    private int line;
    private int column;
    Position(int line, int column) {
      this.line = line;
      this.column = column;
    }
  }
}

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// Correct
class Log {
  static class Position {
    private int line;
    private int column;
    Position(int line, int column) {
      this.line = line;
      this.column = column;
    }
  }
}

Answer 3

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Answer 4

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Answer 5

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