How Can I Get Exception in my try catch in Java?

Question

So I'm making a program and I want an exception, so the program wont crash.
If the user puts a string that is not in the else if statements then it would not crash.

Also, I tried doing that for the integer, so if someone tries to write something that is not an integer it wont crash. And the program will catch it and would say that it isn't an integer.

How can I get exception in my try catch in java.

Thank for your help

Here is the code:

import java.util.InputMismatchException;
import java.util.Scanner; 


public class WeightOnADifferentPlanet { 
public static void main ( String[] args ){   
 Scanner scan = new Scanner ( System.in ); 


System.out.println("Where do you want to travel:?");
try{
     String planetName = scan.nextLine(); 
 }
 catch(/*need help here*/){
     System.out.println("Please check your spelling");
 }



 System.out.println("Please enter your weight:"); 
 try{
     int weight = scan.nextInt(); 
 }
 catch(InputMismatchException e)
 {
    System.out.println("That is not an integer"); 
 }
 double earthCalculation = weight * 1.0; 
 double jupiterCalculation = weight * (21.0 / 8.0); //check
 double marsCalculation = weight * (3.0 / 8.0); 
 double mercuryCalculation = weight * (3.0 / 10.0); 
 double neptuneCalculation = weight * (11.0 / 10.0); //check 
 double plutoCalculation = weight * (7.0 / 10.0); 
 double saturnCalculation = weight * (6.0 / 5.0); //check
 double uranusCalculation = weight * (9.0 / 10.0); 
 double venusCalculation = weight * (7.0 / 8.0);


 if (planetName.equalsIgnoreCase("Earth")) 
 {
   System.out.println("Your weight on "+planetName+" is: "+earthCalculation+" pounds."); 
 }
 else if (planetName.equalsIgnoreCase("Jupiter"))
 {
   System.out.println("Your weight on "+planetName+" is: "+jupiterCalculation+" pounds."); 
 }
 else if (planetName.equalsIgnoreCase("Mars")) 
 {
   System.out.println("Your weight on "+planetName+" is: "+marsCalculation+" pounds."); 
 }
 else if (planetName.equalsIgnoreCase("Mercury")) 
 {
   System.out.println("Your weight on "+planetName+" is: "+mercuryCalculation+" pounds."); 
 } 
 else if (planetName.equalsIgnoreCase("Neptune")) 
 {
   System.out.println("Your weight on "+planetName+" is: "+neptuneCalculation+" pounds."); 
 }
 else if (planetName.equalsIgnoreCase("Pluto")) 
 {
    System.out.println("Your weight on "+planetName+" is: "+plutoCalculation+" pounds."); 
 }
 else if (planetName.equalsIgnoreCase("Saturn")) 
 {
   System.out.println("Your weight on "+planetName+" is: "+saturnCalculation+" pounds."); 
 }
  else if (planetName.equalsIgnoreCase("Uranus")) 
 {
   System.out.println("Your weight on "+planetName+" is: "+uranusCalculation+" pounds."); 
 } 
   else if (planetName.equalsIgnoreCase("Venus")) 
 {
   System.out.println("Your weight on "+planetName+" is: "+venusCalculation+" pounds."); 

 }


     }
   }    
}

Answer 1

So I ended up fixing it and here is the result. import java.util.InputMismatchException; import java.util.Scanner;

public class WeightOnADifferentPlanet { 
static Scanner scan = new Scanner ( System.in ); 

public static void main ( String[] args ){   



System.out.println("What planet do you want to travela:?");

     String planetName = scan.nextLine(); 



 System.out.println("Please enter your weight:"); 
 int weight = Integer();


 //int weight = scan.nextInt();


 double earthCalculation = weight * 1.0; 
 double jupiterCalculation = weight * (21.0 / 8.0); //check
 double marsCalculation = weight * (3.0 / 8.0); 
 double mercuryCalculation = weight * (3.0 / 10.0); 
 double neptuneCalculation = weight * (11.0 / 10.0); //check 
 double plutoCalculation = weight * (7.0 / 10.0); 
 double saturnCalculation = weight * (6.0 / 5.0); //check
 double uranusCalculation = weight * (9.0 / 10.0); 
 double venusCalculation = weight * (7.0 / 8.0);


 if (planetName.equalsIgnoreCase("Earth")) 
 {
   System.out.println("Your weight on "+planetName+" is: "+earthCalculation+" pounds."); 
 }
 else if (planetName.equalsIgnoreCase("Jupiter"))
 {
   System.out.println("Your weight on "+planetName+" is: "+jupiterCalculation+" pounds."); 
 }
 else if (planetName.equalsIgnoreCase("Mars")) 
 {
   System.out.println("Your weight on "+planetName+" is: "+marsCalculation+" pounds."); 
 }
 else if (planetName.equalsIgnoreCase("Mercury")) 
 {
   System.out.println("Your weight on "+planetName+" is: "+mercuryCalculation+" pounds."); 
 } 
 else if (planetName.equalsIgnoreCase("Neptune")) 
 {
   System.out.println("Your weight on "+planetName+" is: "+neptuneCalculation+" pounds."); 
 }
 else if (planetName.equalsIgnoreCase("Pluto")) 
 {
    System.out.println("Your weight on "+planetName+" is: "+plutoCalculation+" pounds."); 
 }
 else if (planetName.equalsIgnoreCase("Saturn")) 
 {
   System.out.println("Your weight on "+planetName+" is: "+saturnCalculation+" pounds."); 
 }
  else if (planetName.equalsIgnoreCase("Uranus")) 
 {
   System.out.println("Your weight on "+planetName+" is: "+uranusCalculation+" pounds."); 
 } 
   else if (planetName.equalsIgnoreCase("Venus")) 
 {
   System.out.println("Your weight on "+planetName+" is: "+venusCalculation+" pounds."); 

 }
   else {
       System.out.println("Planet not recognized");
   }
 }



 public static int Integer(){
      while (true)
      {
       try
       {
        return scan.nextInt();
       }
       catch (InputMismatchException e)
       {
           scan.next();
           System.out.print("That’s not an integer. Try again: ");
       }

}
}
}

Answer 2

You don't really need to use exceptions. You can enter anything for planet and it won't crash, since you are checking for nextLine(). For weight, just check if scan.hasNextInt() before setting the weight.

import java.util.Scanner; 


public class WeightOnADifferentPlanet { 
    public static void main ( String[] args ) {   
        Scanner scan = new Scanner(System.in); 

        System.out.print("Where do you want to travel? ");
        String planetName = scan.nextLine(); 

        System.out.print("Please enter your weight: ");
        int weight = 0;
        if (scan.hasNextInt()) {
            weight = scan.nextInt();

            double earthCalculation = weight * 1.0; 
            double jupiterCalculation = weight * (21.0 / 8.0); //check
            double marsCalculation = weight * (3.0 / 8.0); 
            double mercuryCalculation = weight * (3.0 / 10.0); 
            double neptuneCalculation = weight * (11.0 / 10.0); //check 
            double plutoCalculation = weight * (7.0 / 10.0); 
            double saturnCalculation = weight * (6.0 / 5.0); //check
            double uranusCalculation = weight * (9.0 / 10.0); 
            double venusCalculation = weight * (7.0 / 8.0);

            if (planetName.equalsIgnoreCase("Earth")) {
                System.out.println("Your weight on " + planetName + " is: " + earthCalculation + " pounds."); 
            } else if (planetName.equalsIgnoreCase("Jupiter")) {
                System.out.println("Your weight on " + planetName + " is: " + jupiterCalculation + " pounds."); 
            } else if (planetName.equalsIgnoreCase("Mars")) {
                System.out.println("Your weight on " + planetName + " is: " + marsCalculation + " pounds."); 
            } else if (planetName.equalsIgnoreCase("Mercury")) {
                System.out.println("Your weight on " + planetName + " is: " + mercuryCalculation + " pounds."); 
            } else if (planetName.equalsIgnoreCase("Neptune")) {
                System.out.println("Your weight on " + planetName + " is: " + neptuneCalculation + " pounds."); 
            } else if (planetName.equalsIgnoreCase("Pluto")) {
                System.out.println("Your weight on " + planetName + " is: " + plutoCalculation + " pounds."); 
            } else if (planetName.equalsIgnoreCase("Saturn")) {
                System.out.println("Your weight on " + planetName + " is: " + saturnCalculation + " pounds."); 
            } else if (planetName.equalsIgnoreCase("Uranus")) {
                System.out.println("Your weight on " + planetName + " is: " + uranusCalculation + " pounds."); 
            } else if (planetName.equalsIgnoreCase("Venus")) {
                System.out.println("Your weight on " + planetName + " is: " + venusCalculation + " pounds."); 
            } else {
                System.out.println("Planet not recognized");
            }
        } else {
            System.out.println("Invalid weight");
        }
        scan.close();
    }
}

Answer 3

There are several things wrong with your program:

• String planetName needs to be declared outside of the try block.

• You shouldn't have planetName = scan.nextLine(); in a try/catch. You should figure out a way to keep asking the user for a planet name until they get a proper one.

• Also, the int weight needs to be declared outside of the try block.

• Same thing here, you need to figure out a way to keep asking the user for an integer if they don't give you one (e.g. you get an exception).

EDIT: As suggested by MasterBlaster, you should also close out your scanner with scan.close()

Answer 4

I believe scan.nextInt(); will only scan an integer anyways, so there shouldn't be any need to catch non integers