So this is my university assignment which I got pretty much everything done. It is supposed to use method overriding, which I have to do from my class SafeRidingMower (will insert code after explanation) which extends from my professor's class (which I CANNOT change a single thing) RidingMower.
RidingMower Class:
import java.util.*;
/**
* The riding mower class developed by the engineering department. Contains all the functionality needed
* for a working riding mower.
*
*/
public class RidingMower {
private boolean rider_in_seat = false;
private boolean is_engine_on = false;
private boolean is_mower_enabled = false;
private Random rn = new Random();
/**
* Constructor for Riding Mower which automatically launches the main menu.
*/
public RidingMower()
{
mainMenu();
}
/** Starts the engine of the riding mower (ignition start) */
public void start_engine()
{
System.out.println("<<< Starting riding mower >>>");
is_engine_on = true;
}
/** Method that randomly seats and unseats a driver */
private void sit_rider()
{
int random = rn.nextInt(5);
if ( random<=1 )
rider_in_seat = true;
else rider_in_seat = false;
System.out.print("\t=>Seated? " + rider_in_seat + "\n");
}
/** Seat sensor. Returns true if there is a driver seated on the mower or false
* if no driver is sitting on the mower.
* @return
*/
public boolean check_seat_sensor()
{
return rider_in_seat;
}
/** Method that engages the mower blades and begins mowing if the ignition is turned on */
public void mow()
{
start_mowing();
}
/** Primary method that handles the mowing. Checks to see if the ignition is on then the
mowing starts otherwise the cutting blades are lowered and ready to mow upon engine start
*/
private void start_mowing()
{
is_mower_enabled = true;
System.out.println("Mower blade ready to mow");
if ( !is_engine_on ) return;
int i=1;
while (true)
{
mowing(i++);
}
}
/** Mower fully functioning here and blades are spinning. Simulates a rider being thrown off
the mower at step 50,000 */
private void mowing(int i)
{
System.out.println( "Mowing..." + i);
if ( i>50000 ) rider_in_seat = false;
if ( rider_in_seat == false )
System.out.println("\tOMG Mower is moving without a driver?!");
mowing_hook();
}
/** Hook/Stub function called while the mower is mowing. Other departments divisions can override */
public void mowing_hook()
{
}
/** Turns off the ignition. Stops the mower if running. */
public void stop_mower()
{
System.out.println("Stopping the mower.");
System.exit(0);
}
/** Main menu of the mower simulation. Asks user to check/seat a driver, start the mower,
* begn mowing the lawn, or exiting the simulation. Method is private and can not be
* overriden.
*/
private void mainMenu()
{
Scanner sc = new Scanner( System.in );
int option;
do
{
System.out.println();
System.out.println("1. Is driver seated? (" + rider_in_seat +")" );
System.out.println("2. Start mower");
System.out.println("3. Mow the lawn");
System.out.println("4. Stop mower (if running) and Exit.");
System.out.println();
System.out.println("CHOOSE 1-4");
option = sc.nextInt();
switch ( option )
{
case 1: sit_rider();
break;
case 2: start_engine();
if ( is_mower_enabled ) mow();
break;
case 3: mow();
break;
case 4: stop_mower();
break;
}
} while ( true ); // Infinite loop here. Select option #4 to exit the program.
}
}
SafeRidingMower Class:
public class SafeRidingMower extends RidingMower
{
@Override
public void start_engine() {
if (check_seat_sensor() == true)
super.start_engine();
else
System.out.println("Seat sensor does not detect a driver."
+ "Engine will not start.");
}
@Override
public boolean check_seat_sensor() {
return super.check_seat_sensor();
}
@Override
public void mow() {
if (check_seat_sensor() == true)
super.mow();
else if (check_seat_sensor() == false)
System.out.println("Seat sensor does not detect a driver."
+ " Mower will not start.");
else
System.out.println("Engine is not on. Cannot start mowing.");
}
@Override
public void mowing_hook() {
}
}
And the Driver, which I assume it's not relevant for the specific issue I'm having, but here it is anyway.
public class TheLawnMowerManDriver {
public static void main(String[] args)
{
RidingMower mower = new SafeRidingMower();
}
}
What I need to do: in the RidingMower class, there is the method mowing() which I cannot override, but I can override the method mowing_hook() which is called at the end of the method mowing(). What I'm supposed to do is to stop the lawnmower from running when the variable i = 50000, but I have no idea how to do so. I tried using the super keyword with the variable, but it didn't work (I don't know if it was supposed to work or not, I was only introduced to the super keyword a few classes ago).
Does anyone know a way that I can stop the lawnmower/stop the variable i from counting from overriding the mowing_hook() method?
I found a solution for this problem.
As I said, I believe that or you missunderstood the problem or your professor is tricking you.
Anyway, it is possible to stop the execution if we watch the mowing() method execution indirectly.
The idea is to wrapper the System.out and record the last string that was printed. So, in mowing_hook() we can see watch was printed and stop when necessary.
You can find a working example here: jdoodle.com/a/12KZ
In summary:
Add this class to you code
class SystemOutWrapper extends PrintStream{
String lastLine;
public SystemOutWrapper(OutputStream out){
super(out);
}
@Override
public void println (String str){
this.lastLine = str;
super.println(str);
}
public String getLastLine(){
return lastLine;
}
}
And override the method this way
@Override
public void mowing_hook() {
if (! (System.out instanceof SystemOutWrapper)){
System.setOut(new SystemOutWrapper(System.out));
}
//I used 100 as the online editor limitation. But you should change to 50000
if ("Mowing...100".equals( ((SystemOutWrapper) System.out).getLastLine())){
System.out.println("Limite reached! Should stop now!");
stop_mower();
}
}