Counter class

Question

Counter increases and decreases by 1, records count nonnegative integer and tests whether the current count value is zero. No method allows the value of counter to become negative. Can anyone assist?public class Counter
private int count; // definition of counter
public Counter(int aCount) // Constructor to initialize count
count = aCount;
public void setCountToZero() //method to zero out counter
count = 0;
public void addOneToCount() //method to add one to counter
count += 1; // or count++;
public void subtractOneFromCount() //method to subtract one from counter
if ((count - 1) >= 0)
{count -= 1;} // or count--;     
public void displayCount()
System.out.println("The count is " + count);
//tester
package counter;
public class CounterTest
public static void main(String[] args)
Counter myCounter = new Counter(-1); // Create myCounter Object and give 10 to counter
myCounter.displayCount(); // Displays the zero value
myCounter.addOneToCount(); // Now count has value of 11
myCounter.displayCount(); // Displays the zero value
myCounter.subtractOneFromCount(); // Subtracted one from count
myCounter.displayCount(); // Displays count
myCounter.setCountToZero(); // Resets count to zero
myCounter.displayCount(); // Displays the zero value
}

Answer 1

In Java it's normal not to decorate argument names (or any other names for that matter), so call the 'count' argument 'count'. If there's an ambiguity with a field of an object, use 'this.' to indicate the field. Making the argument final prevents any assignment, which would be an error - it's only use is to input a value to the constructor.
If a negative value is an illegal value for the argument, then throw an IllegalArgumentException instead of trying to guess the correct value (so far guesses have been 'the client requested -17, perhaps he meant zero' and 'the client requested -2147483648, perhaps he meant, err, -2147483648' ( abs(-2147483648) == -2147483648 as signed 32 bits doesn't have a [phone]) ) - something is trying to create a counter with a negative count, and that is a bug, so making it show up as an exception means you find the bug earlier.
public Counter (final int count) {
  if (count < 0)
    throw new IllegalArgumentException("Count must be greater than or equal to zero: " + count);
  this.count = count;
}