Question

Define a class called Counter whose internal "count" variable is a basic integer counter. This class track that count from its instantiation in the constructor (can be set to any positive integer, or 0). The count should never be allowed to be negative. Include methods that will set the counter to 0, increase the count by 1, and decrease the count by 1.

Include an accessor method that returns the current count value (getCount()). There should be no input / setter method or other mutator methods. The only method that can set the counter is the one that sets it to zero (and the constructor).

This class should also override the Object class toString() and equals() methods - refer to the Java APIs for more guidance on how to override this (Chapter 8 also describes this in a little detail, but the API may be more useful): https://docs.oracle.com/javase/10/docs/api/java/lang/Object.html Finally, write a main method (in this class) to test all the methods in your class definition.

Answer 1

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Program Code to Copy

class Counter {
    int count;

    //Argumented constructor
    Counter(int count) {
        this.count = count;
    }

    //Accessor
    public int getCount(){
        return this.count;
    }

    //Increment and decremenet
    void increment() {
        this.count++;
    }

    void decrement() {
        if (this.count > 0)
            this.count--;
    }

    //Reset count to 0
    void reset() {
        this.count = 0;
    }

    @Override
    public String toString(){
        return "(Count : "+this.count+")";
    }

    @Override
    public boolean equals(Object obj){
        Counter c = (Counter) obj;
        return this.count == c.count;
    }
}


class Main {
    public static void main(String[] args) {
        Counter c = new Counter(5);
        System.out.println(c);
        c.increment();
        c.increment();
        System.out.println(c);
        Counter d = new Counter(8);
        d.decrement();
        System.out.println(c+" == "+d+" : "+c.equals(d));
        c.reset();
        System.out.println("C reset. Count is "+c);
    }
}