I want to make sure about abstract classes issue

Question

Hello,
I have an interface with two methods.
interface call{
void trial (int p);
void show();
And an abstract class that implements that interface with overriding only one method of the two.
abstract class client implements call {
public void trial(int num) { System.out.println(num);}
In the main method, I wanted to instantiate the implementing class in order to make use of the one method it overrides, but I received an error that the class as abstract, cannot be instantiated.
class test{
public static void main(String args[]) {
//creating object reference to the implementing class
client c = new client(); //the error is here
c.trial(5);
//creating an interface reference
call m = new client(); //also doesn't work
m.trial(5);
So does I understand from this that if a class does not provide full implementation of an interface (i.e. abstract class), it cannot be used inside my program?
Thanks!

Answer 1

Please use code tags (see CODE button above posting box). Also, please use standard Java conventions of using a capital letter to start a class name.
You are getting that error message because you didn't define show, and the interface requires it. You have to extend the Client abstract class to define show.
You can make an anonymous class that defines show:
Call m = new Client() {
   public void show() {
      System.out.println("Do something.");
m.trial(5);Or, you can make a non-anonymous class that defines show:
class MyClient extends Client {
   public void show() {
}In this example, "show" doesn't actually do anything, but it does satisfy the interface. You can put the same "show" as I put in my anonymous class, or you can do whatever you want in "show".
Then, in your "main", you'd have:
MyClient client = new MyClient();
client.trial(5);
//or
Call anotherClient = new MyClient();
anotherClient.trial(6);
//or
Client yetAnotherClient = new MyClient();
yetAnotherClient.trial(7);