Instance variables

[jwl]

Hello,

I am going through "Java Concepts 6th Edition" by Cay Horstmann and I am having trouble With creating a new counter and a couple of other things. Here is the code from chapter 3.

import sun.management.counter.Counter;

public class counter {
        private int value = 4;
        Counter tally = new Counter(); //Error Counter is Abstract; cannot be instantiated
        tally.count();                 //Error package tally DNE
        tally.count();                 //Error packege tally DNE                         
        int result = tally.getValue(); //Error Incomparable types required int
                                       //      found java.lang.Object
        public void count(){
            value = value + 1;
        }  
        
        public int getValue() {
            return value;
        }
    }

I think I know why the tally isn't working(this is all the code I have for this problem) but I don't know why the counter isn't working since I did something similar to this in chapter 2.

// from chapter 2
JavaApplication63 component = new JavaApplication63();
        frame.add(component);

Can someone please help with this

[quad64bit]

Why do you have a class called "counter" and a class you import called "Counter"? Java is case sensitive, and class names should never be lower case. I also don't understand how this code even compiles, since you cannot call methods outside of a method body...

[SJF]

Well, for staters if Counter is an abstract class, you'll have to create a class that implements Counter, and instantiate that class...

   public class MyCounter implements Counter{
....
}

ALL abstract methods in Counter then need to be properly implemented.

			@Override
			public int getFlags() {
				throw new UnsupportedOperationException();   //or return 0; or return -2000; doesn't really matter
                                                                                               //what does matter is that the abstract methods are implemented.
			}

You will instantiate YOUR class...

    Counter tally = new MyCounter();