Ok, easy question...About implements and extends

Question

Im sure this will be simple to all of you, but I am still new to the Java language. I want to know the difference between using "extends" and "implements" in the way that its used in these examples:
With the "extends" keyword...
class PrimeThread extends Thread {
         long minPrime;
         PrimeThread(long minPrime) {
             this.minPrime = minPrime;
         public void run() {
             // compute primes larger than minPrime
     }And then with the "implements" keyword...
Using the interface "Runnable"
class PrimeRun implements Runnable {
         long minPrime;
         PrimeRun(long minPrime) {
             this.minPrime = minPrime;
         public void run() {
             // compute primes larger than minPrime
     }Can someone please explain when you would want to use the "extends" version and when you would want to use the "implements" version? Sorry for practically insulting your intelligence...I'm just trying to learn this language without a book as an experiment to see (how much/how fast) I can learn purely using the web resources...Thanks to anyone who wishes to explain this to me.

Answer 1

That's pretty much it.
An interface may extend zero or more other interfaces.
A class (except Object) always extends exactly one other class--either the class explicitly named with "extends", or Object if "extends" is not present.
A class may implement zero or more interfaces.
"Extends" implies a parent-child relationship. Interfaces extend other interfaces, and classes extend other classes.
"Implements" implies a contract stating that the class will provide implementations for all the methods declared in the interface (or the class will be declared abstract). If a class implements A, and A extends B, then that class must implement all methods declared in A and all methods declared in B.
Does this help?