Example: tally counter
Problem: find out how many people attend a concert or board a bus.
Features:
1. Whenever the operator pushes a button, the counter value advances by one. (count
method)
2. A physical counter has a display to show the current value. (getValue
method)
Counter tally = new Counter();
tally.count();
tally.count();
int result = tally.getValue(); // Sets result to 2
3. Each counter needs to store a variable that keeps track of how many times the counter has been advanced
Instance variables
store the data of an
object
Instance of a class:
an
object of the class
The class declaration specifies the instance variables:
Each object
of a class has its own set of instance variables
You should declare all instance variables as private
Supply the body of a method public void reset() that resets the counter back to zero
Answer:
public void reset()
{
value = 0;
}