Comparable interface java 1.5

[Cathy Song]

Hi all,

Could someone please post an example of how
to use the comparable interface with java 1.5?

Thank you.
-Cathy.

[Jeff Langr]

public class EmployeeTest extends junit.framework.TestCase {
   public void testCompare() {
      Employee one = new Employee(1);
      Employee two = new Employee(2);
      assertTrue(one.compareTo(two) < 0);
      assertTrue(two.compareTo(one) > 0);
      Employee onePrime = new Employee(1);
      assertEquals(0, one.compareTo(onePrime));
      assertEquals(0, onePrime.compareTo(one));
   }
}

public class Employee implements Comparable<Employee> {
   private int id;
 
   public Employee(int id) {
      this.id = id;
   }
 
   public int compareTo(Employee that) {
      return id - that.id;
   }
}

Since you bind the interface to the Employee type, the compareTo method signature takes an argument of type Employee.

-Jeff-

[Layne Lund]

I haven't dabbled with Java 5.0 yet, so I have a question related to this thread: can you implement Comparable "bound" to different types? I imagine something like:

class A implements Comparable<A>, Comparable<B>, Comparable<C> {
 // yadda
}

Does this work? (I should probably download Java 5.0 and try it myself. However, I don't want to mess up my development environment at home while I'm in the middle of a big project. I'll definitely look into it next semester, though.)

Layne

[Cathy Song]

Thanks Layne and Jeff

-Cathy.

[Jeff Langr]

You're welcome!

Layne --

The compiler appears to prevent it.

-Jeff-