Exception not thrown

[Kevin O'Sullivan]

Hi, How come the exception error message in the setter method setPrice is never thrown if the price of the car is less than 50,000? the message never appears in the console when the program is run.

import java.io.*;
import java.util.*;
public abstract class Car{
   
   private String carMake;
   private String model;
   private int engineSize;
   private int price;
   
   public Car(String carMake,String model,int engineSize,int price){
      this.carMake = carMake;
      this.model = model;
      this.engineSize = engineSize;
      this.price = price;
   }
   public void setCarMake(String carMake){
      this.carMake = carMake;
   }
   public String getCarMake(){
      return this.carMake;
   }
   public void setModel(String model){
      this.model = model;
   }
   public String getModel(){
      return this.model;
   }
   public void setEngineSize(){
      this.engineSize = engineSize;
   }  
   public int getEngineSize(){
     return this.engineSize;
   }
   public void setPrice(int price) {
     if(price < 50000){
       throw new IllegalArgumentException("Error");
       }else{  
       this.price = price;
       } 
   }
   public int getPrice(){
      return this.price;
   }
   public abstract void move();
   
   public String toString(){
     return("********************\n"+
            "*     Car Model    *\n"+
            "*      Details     *\n"+
            "********************\n"+
            "Car Make: " +carMake 
            +"\n"
            +"Model: " + model
            +"\n"
            +"Engine Size: " + engineSize
            +"\n"
            +"Price: " + price );
   }
   
   

}

public class CarType1 extends Car{
  
  private boolean powerSteering;
  
  public CarType1(String carMake,String model,int engineSize,int price,boolean powerSteering){
    super(carMake,model,engineSize,price);
    this.powerSteering = powerSteering;
  }
  public void setIsPowerSteering(boolean powerSteering){
     this.powerSteering = powerSteering;
  }
  public boolean getPowerSteering(){
     return this.powerSteering;
  }
  public void move(){
    System.out.println("A car moves,vroom vroom! ");
  }
  public String toString(){
    return(super.toString()
           +"\nPower Steering: " + powerSteering);
  }
}

import java.io.*;
import java.util.*;

public class Car_Tester{
   public static void main (String[] args){
    
      CarType1 c1 = new CarType1("B.M.W","Series 7",100,0,true);
      System.out.println(c1.toString());
      c1.move();
            
   }
}

Thank you.

[Knute Snortum]

I would guess because the method setPrice() is never called.  You can test that by putting a System.out.println() as the first line of the method.  But notice that when you create the Car object, you don't use setPrice().

[Kevin O'Sullivan]

Got it working,bye adding the set method to the constructor.

public Car(String carMake,String model,int engineSize,int price){
		this.carMake = carMake;
		this.model = model;
		this.engineSize = engineSize;
		this.setPrice(price);
		
	}

Exception in thread "main" java.lang.IllegalArgumentException: Error price too high!
at Car.setPrice(Car.java:42)
at Car.<init>(Car.java:14)
at CarType1.<init>(CarType1.java:7)
at Car_Tester.main(Car_Tester.java:7)

Is there anyway for to just print out the Error message "Error price too high !" instead of the rest ?

[Campbell Ritchie]

You will have to alter the setPrice() method because you are calling a public method from the constructor. Methods called from the constructor should be private or final (no need to be both). By writing a setXXX() method, you are making it difficult to make the object immutable.

[Knute Snortum]

Is there anyway for to just print out the Error message "Error price too high !" instead of the rest ?

Well, you could just use System.out.println() and then call System.exit(1), but I think the exception is the way to go.  

[Kevin O'Sullivan]

Campbell Ritchie wrote:You will have to alter the setPrice() method because you are calling a public method from the constructor. Methods called from the constructor should be private or final (no need to be both). By writing a setXXX() method, you are making it difficult to make the object immutable.

I'm not sure I understand could you give an example?

[Campbell Ritchie]

public final void setPrice(int price) {   if(price < 50000){      throw new IllegalArgumentException("Error");   }else{        this.price = price;   } }That prevents nasty surprises if anybody tries to override that method in a subclass.
Please space your code out more: one empty line between successive methods, please. Please also consider whether you need all those setXXX() methods, but setPrice() is the one you would want to retain if you retain any setXXX() methods at all.

[Kevin O'Sullivan]

Could you catch it with a try/catch in your tester class? and if you can how would you do it?

                 CarType1 c1 = new CarType1("B.M.W","Series 7",100,51000,true);
                 System.out.println(c1.toString());
                 c1.move();

[Campbell Ritchie]

Kevin O'Sullivan wrote:Could you catch it with a try/catch in your tester class? and if you can how would you do it?

Car c = null;
do
{
   try
   {
      c = new Car(KeyboardInputs.nextLine("Enter make: "),
                  KeyboardInputs.nextLine("Enter model: "),
                  KeyboardInputs.nextInt("Enter engine cc: "),
                  KeyboardInputs.nextInt("Enter price: "));
   }
   catch (IllegalArgumentException ex)
   {
      System.err.println(ex.getMessage());
   }
} while (c == null);
System.out.println(c); // No need to say toString().

At which point you realise that you should have used a more informative error message for your exception. As a general rule of thumb, you shouldn't catch unchecked exceptions, but this looks like a situation where that is a reasonable thing to do. There are much more elegant ways to create such Cars; the nextInt() method is overridden so as only to return values in a pre‑defined range, so you can avoid the exception altogether. I shall let you work out how the KeyboardInputs class works.

[Kevin O'Sullivan]

Thanks for that!