Problem

This program simulates a radar trap for catching people who are driving over the speed limit. We will use JOptionPane.showInputDialog for input and JOptionPane.showMessageDialog for output, and all inputs will be integers. The user will first enter the speed limit for the road being monitored, and all subsequent inputs will be the speed of each vehicle that passes through the radar trap. An input of -1 ends the program.

If a vehicle is travelling at or under the speed limit, print a message stating that the vehicle is within the speed limit. Otherwise, if the vehicle is over the speed limit by 20 km/hr or less, the driver gets a $40 speeding ticket. If the vehicle is over by more than 20 km/hr and less than or equal to 40 km/hr, the driver gets an $80 ticket. If the vehicle is over by more than 40 km/hr, the driver gets a $120 ticket. If the vehicle is over the speed limit, print a message stating by how much the vehicle is over the speed limit, and the amount of the speeding ticket for that vehicle.

In addition, for every 10 cars that are caught, the police officer on duty receives a $20 bonus. You will need to keep track of this total as well, separately from the speeding tickets.

Once the program has ended, it should print the total number of cars caught speeding, the total amount of fines issued, and the total amount of the police officer's bonus.

String Methods & Debugging

Solution

1. First declare the necessary variables.

//variable declarations
int speedLimit;
int speed = 0;
int amountOverLimit = 0;
int ticket = 0;
int ticketTotal = 0;
int bonus = 0;
int vehicleCount = 0;
String input = "";

2. The first input dialog comes up asking for the speed limit of the road.
The input string must be parsed to an int.

input = JOptionPane.showInputDialog("Enter the speed limit for the road.");
speedLimit = Integer.parseInt(input);

3. Now the main loop begins. The user is asked to enter the current vehicle's speed, and the loop repeats as long as the user
does not enter -1. The input string must again be parsed to an int.

while (speed != 1)
{
    input = JOptionPane.showInputDialog("Speed of current vehicle is");
    speed = Integer.parseInt(input);
    amountOverLimit = speed - speedLimit;

4. First check if the vehicle is within the speed limit. If it is, print a message confirming this.

if(amountOverLimit <= 0)
{
	ticket = 0;
	JOptionPane.showMessageDialog("Vehicle is within the speed limit.");
} 

5. If the vehicle is speeding, check by how much it is speeding and ticket the driver for the appropriate amount.
Print a message with this information.

else
{
	if(amountOverLimit > 40)
	{
	    ticket = 120;
	}
	else if(amountOverLimit > 20)
	{
  	    ticket = 80;
	}
	else
	{
	    ticket = 40;
	}
	
	JOptionPane.showMessageDialog("Vehicle is " + (amountOverLimit) + "over the limit. " +
        "The fine is $" + fine + ".");

6. Add the amount of the ticket to the total ticket amount, and increment the number of speeding vehicles.
Close the else block opened in Step 5 and the while loop opened in Step 3.

	    ticketTotal += ticket
	    vehicleCount++;
    } //end else
} //end while

7. Calculate the police officer's bonus.

bonus = (carCount/10) * 20;

8. A final message dialog appears that states how many cars were speeding, the total amount of fines issued, and the total amount of the police officer's bonus.

JOptionPane.showMessageDialog("A total of $" + ticketTotal + " in speeding tickets were issued for" + 
totalVehicles +  " vehicles. The officer receives a $" + bonus + " bonus.");

Code

Solution Code

import javax.swing.*;

public class RadarTrap
{
	public static void main(String[] args)
	{
		//variable declarations
		int speedLimit;
		int speed = 0;
		int amountOverLimit = 0;
		int ticket = 0;
		int ticketTotal = 0;
		int bonus = 0;
		int vehicleCount = 0;
                String input = "";
	
		//read in the speed limit from the input dialog	
		input = JOptionPane.showInputDialog("Enter the speed limit for the road.");
                speedLimit = Integer.parseInt(input);		
 
		while(speed != -1)
		{
			input = JOptionPane.showInputDialog("Speed of current vehicle is");
                        speed = Integer.parseInt(input);
			amountOverLimit = speed - speedLimit;
			
			//first check if the vehicle is over the speed limit
			if(amountOverLimit <= 0)
			{
				ticket = 0;
				
				JOptionPane.showMessageDialog("Vehicle is within the speed limit.");
			}
			//if so, check by how much and determine the amount of the ticket
			else
			{
				if(amountOverLimit > 40)
				{
					ticket = 120;
				}
				else if(amountOverLimit > 20)
				{
					ticket = 80;
				}
				else
				{
					ticket = 40;
				}
				
				JOptionPane.showMessageDialog("Vehicle is " + (amountOverLimit) + "over the limit. The fine is $" + fine + ".");

				ticketTotal += ticket
				vehicleCount++;
			}
		}
		
		bonus = (carCount/10) * 20;
		
		JOptionPane.showMessageDialog("A total of $" + ticketTotal + " in speeding tickets were issued for" + totalVehicles +  " vehicles. "
					+ "The officer receives a $" + bonus + " bonus.");
	}
}