Refactoring generic compareTo method

What am I doing:

I have a container class named Os, that can contains different type elements and also instances of class Os. When I compare this class, I want to see :

• shallow equals for elements
• deep equals for Os elements

I have ensured, that every single element contained in class:

• Can not be null.
• Is comparable to same type elements.
• Is immutable. Well, at least part that I'm checking.

Following is what I have at the moment.

Example:

For example, this test case will pass.

    Os o1 = Os.of(3, 4d, Os.of("-"));
    Os o2 = Os.of(Os.of(Character.toString('-')), 4.0, new Integer(3));

    assertEquals(o1.toString(), "[3, 4.0, [-]]");
    assertEquals(o2.toString(), "[[-], 4.0, 3]");
    assertTrue(o1.reverse().compareTo(o2) == 0);

Code example:

compareTo method:

@Override
public int compareTo(final Os that) {
    final int BEFORE = -1;
    final int EQUAL = 0;
    final int AFTER = 1;
    int subresult = 0;
    Comparable<?> othis;
    Comparable<?> othat;

    if (that == null)
        return AFTER;
    if (this == that)
        return EQUAL;

    subresult = ((Integer) this.o.size()).compareTo(that.o.size());
    if (subresult < 0)
        return BEFORE;
    else if (subresult > 0)
        return AFTER;

    try {
        for (int i = 0; i < this.o.size(); i++) {
            othis = this.o.get(i);
            othat = that.o.get(i);

            if (othis.getClass() == othat.getClass()) {
                if (othat instanceof Os) {
                    subresult = ((Os) othis).compareTo(((Os) othat));
                    if (subresult < 0)
                        re开发者_运维百科turn BEFORE;
                    else if (subresult > 0)
                        return AFTER;
                } else {
                    subresult = hackCMP(othis, othat);
                    if (subresult < 0)
                        return BEFORE;
                    else if (subresult > 0)
                        return AFTER;
                }
            } else {
                subresult = othis.getClass().getName()
                        .compareTo(othat.getClass().getName());
                if (subresult < 0)
                    return BEFORE;
                else if (subresult > 0)
                    return AFTER;
            }
        }
        return EQUAL;
    } catch (SecurityException e) {
        e.printStackTrace();
    } catch (IllegalArgumentException e) {
        e.printStackTrace();
    } catch (NoSuchMethodException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    } catch (InvocationTargetException e) {
        e.printStackTrace();
    }
    return BEFORE;
}

private static int hackCMP(Object val, Object val2)
        throws SecurityException, NoSuchMethodException,
        IllegalArgumentException, IllegalAccessException,
        InvocationTargetException {
    Method m = val.getClass().getMethod("compareTo", val.getClass());
    return (Integer) m.invoke(val, val2);
}

Question:

I would like to refactor the code.

For example:

• I would prefer not using hackCMP method, if possible.

• Following code segment seems to repeat itself a lot. Can I replace it with something?

          subresult = <expression>;
          if (subresult < 0)
              return BEFORE;
          else if (subresult > 0)
              return AFTER;
          //else ...
  

What can I refactor and how to do it?

Edit:

@wolfcastle : Data is stored in private final ImmutableList<Comparable<?>> o;.

I'd like to mention, that every answer was useful. Following seems to work:

@Override
public int compareTo(final Os that) {
    Ordering<Iterable<Comparable<?>>> order = //
    Ordering.natural().<Comparable<?>> lexicographical();
    int result = -1;

    try {
        result = ComparisonChain.start()
                .compare(this.o.size(), that.o.size())
                .compare(this.o, that.o, order).result();
    } catch (Exception e) { //ignore: type mismatch
    }

    return result;
}

---

One option I would consider would be storing the elements in a class that allows them to be compared by class rather than by their compareTo method if they aren't the same class:

private static class Element implements Comparable<Element> {
  // raw Comparable allows you to call compareTo
  private final Comparable comparable;

  Element(Comparable comparable) {
    this.comparable = comparable;
  }

  @Override @SuppressWarnings("unchecked")
  public int compareTo(Element o) {
    Comparable other = o.comparable;
    if(comparable.getClass().isInstance(other)) {
      return comparable.compareTo(other);
    }

    return comparable.getClass().getName().compareTo(other.getClass().getName());
  }

  @Override
  public boolean equals(Object obj) {
    return obj instanceof Element && comparable.equals(((Element) obj).comparable);
  }

  @Override
  public int hashCode() {
    return comparable.hashCode();
  }

  @Override
  public String toString() {
    return comparable.toString();
  }
}

Then, with your internal list being a List<Element>, your compareTo method in Os could be pretty simple. Using Guava, it could be extremely simple:

@Override
public int compareTo(Os o) {
  return ComparisonChain.start()
       .compare(list.size(), o.list.size())
       .compare(list, o.list, Ordering.natural().<Element>lexicographical())
       .result();
}

---

You could have a method that returned BEFORE | AFTER | INDETERMINATE (say), then call it.

result = newMethod(subresult);
if (result != INDETERMINATE) return result;

That's not much of an improvement, and it still needs to be duplicated everywhere, but it's a little tighter.

---

Since the generic type of the List<Comparable<?>> o property is not fixed, I'd get rid of the generic type and rely on the raw type. It costs one @SuppressWarnings("rawtypes"), but it minimizes a lot.

@Override
@SuppressWarnings("rawtypes")
public int compareTo(final Os that) {
    final int BEFORE = -1;
    final int EQUAL = 0;
    final int AFTER = 1;

    if (that == null)
        return AFTER;
    if (this == that)
        return EQUAL;

    int subresult = ((Integer) this.o.size()).compareTo(that.o.size());

    if (subresult != EQUAL)
        return subresult;

    for (int i = 0; i < this.o.size(); i++) {
        Comparable othis = this.o.get(i);
        Comparable othat = that.o.get(i);
        subresult = othis.compareTo(othat);

        if (subresult != EQUAL)
            return subresult;
    }

    return EQUAL;
}