JAVAにおけるstaticメソッド

public abstract class Calculator {
  protected abstract int getValue(Object o);

  public final int getSum(Collection c) {
    int sum = 0;
    for (Iterator it = c.iterator(); it.hasNext(); ) {
      sum += getValue(it.next());
    }
    return sum;
  }
}

public class A {
  private static final Calculator A_CALCULATOR = new Calculator() {
    protected int getValue(Object o) {
      return ((A)o).getHoge();
    }
  };

  public static Calculator calculator() {
    return A_CALCULATOR;
  }

  public int getHoge() {
    ...
  }
}

public class ACalc extends Calculator {

    protected int getValue(Object o) {

      return ((A)o).getHoge();

    }

}



public class A {

  ...

  public int getHoge() {

    ...

  }

}



public class ATestCase extends TestCase {

  public ATestCase(String name) {

    super(name);

  }



  public void testCtg() throws Exception {

    A aObj = new A(1);

    ...

    AList aList = new AList();

    ACalc calc = new ACalc();

    assertTrue("calc.getSum(aList)", 0 < calc.getSum(aList));

  }

}