Implementing Comparable in an abstract class

Question

Hi all,
I am making my first sortie with abstract classes. I have had a good look around, but would still appreciate some advice with the following problem.
In my application I have several classes that have many things in common. I have concluded therefore, that if I create and then inherit from an abstract super class, I can reduce and improve my code. I created this abstract class:
public abstract class YAbstractObject implements Comparable {
    public YAbstractObject(int projectId, YObject object, String objectName) {
        this.projectId = projectId; // Always the same parameters
        this.object = object;
        this.objectName = objectName;
    // This is abstract as it must always be present for sub classes but differant processing will take place
    public abstract void resolveObject();
    // These three methods will always be the same for all sub classes
    public String getName() {
        return objectName;
    public YObject getObject() {
        return object;
    public boolean isValid() {
        return isValid;
// Overridden and always the same for all sub classes
    public String toString() {
        return objectName;
    // implemented abstract method
    public int compareTo(Object thatObject) {
        // Issue here! I would like something as follows:
        //  return this.getName().compareToIgnoreCase(thatObject.getName());
// Variable decleration
    private int projectId;
    private YObject object;
    private String objectName;
    private boolean isValid;As I have commented in the compareTo() method, I would like it to be able to use the getName() method for comparison objects and compare them. But it does not like this, as it does not know that "thatObject" is of the same class as this object - I hope that made sense.
in essence, I want to inherit this method for different classes and have it work with each.
Is there a way to do this? Generics?
Any observations, greatly appreciated,
Steve

Answer 1

You can use also generics (if applicable: java -version >= 1.5).
public abstract class Test implements Comparable<Test> {
     String name;
     public Test(String name) {
          this.name = name;
     public String getName() {
          return name;
     public int compareTo(Test obj) {
          return this.getName().compareTo(obj.getName());
public class Other extends Test {
     public Other(String name) {
          super(name);
public class Tester extends Test {
     public Tester(String name) {
          super(name);
     public static void main(String[] args) {
          Test t = new Tester("t");
          Test a = new Tester("a");
          Test o = new Other("t");
          System.out.println(t.compareTo(a));
          System.out.println(t.compareTo(new Object())); //compile error
          System.out.println(t.compareTo(o));
}Without the compile error line it will give the following result:
19
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