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Thread: My first functioning Try Catch program

  1. #1
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    Default My first functioning Try Catch program

    I have chosen a do-while loop mechanism for my first try catch Java program, but it's kind of a mess:

    package sam;
    import java.text.DecimalFormat;
    import java.text.NumberFormat;
    import java.util.Scanner;
     
    public class Test {
     
    	public static void main(String[] args){
    		System.out.println("Lets play with some try catch statements.");
    		Scanner input = new Scanner(System.in);
    		int x=1, num1=1, num2=1;
     
    		do{
    			try{				
    				System.out.println("Enter the first (dividend) int: ");
    				num1 = input.nextInt();
    				int parsedNum1 = Integer.parseInt(num1);
    				System.out.println("Enter the second (divisor) int: ");
    				num2 = input.nextInt();	
    				int parsedNum2 = Integer.parseInt(num2);
     
    				int quotient = num1 / num2;//dividend / divisor
    				System.out.println("Our quotient is: " + quotient);
     
    				x = 2;//when the user enters proper input, change x, so that the while condition below can terminate our do while loop.				
    			}
    			catch(NumberFormatException e){
    				//check if num1 is an integer
    				//check if num2 is an integer
    				//statement to catch a NumberFormatException?
     
    				System.out.println("Error. Invalid dividend or divisor. Please try again.");
    				continue;
     
    			}
    		}while(x==1);		
     
    	}//end of main
    }//end of class Test

    Lines 17 and 20 keep throwing the same error, "The method parseInt(String) in the type Integer is not applicable for the arguments (int)".

    I don't understand how the "e" parameter works in line 27's catch statement. Does it have to be "e" for a special reason? Would it still work if I used "fred" for the parameter instead?

    I'm unsure how to proceed making exception handlers. Am I just supposed to use a bunch of if statements? Do I need to use the continue statement in a do-while loop?

  2. #2
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    Default Re: My first functioning Try Catch program

    The method parseInt(String) in the type Integer is not applicable for the arguments (int)".
    The parseInt method takes a String value as its argument, not an int value. There would be no need to convert/parse an int value to an int value.
    catch(NumberFormatException e)
    how the "e" parameter works in line 27's catch statement
    It is like the definition of an argument for a method.
    NumberFormatException is the type and e is the name. You can use any name you want. fred would work.

    Note: x is a poor name for a variable that is used to control a loop. Variable names should reflect what kind of values they hold. For the specific case, the variable has 2 values which means a boolean variable could be used. For example stayInLoop would be true to start with and changed to false when the code wants to exit the loop.
    Another possibility would be to use a break statement to exit the loop.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: My first functioning Try Catch program

    Quote Originally Posted by SamJava_the_Hut View Post
    I have chosen a do-while loop mechanism for my first try catch Java program, but it's kind of a mess:

    package sam;
    import java.text.DecimalFormat;
    import java.text.NumberFormat;
    import java.util.Scanner;
     
    public class Test {
     
    	public static void main(String[] args){
    		System.out.println("Lets play with some try catch statements.");
    		Scanner input = new Scanner(System.in);
    		int x=1, num1=1, num2=1;
     
    		do{
    			try{				
    				System.out.println("Enter the first (dividend) int: ");
    				num1 = input.nextInt();
    				int parsedNum1 = Integer.parseInt(num1);
    				System.out.println("Enter the second (divisor) int: ");
    				num2 = input.nextInt();	
    				int parsedNum2 = Integer.parseInt(num2);
     
    				int quotient = num1 / num2;//dividend / divisor
    				System.out.println("Our quotient is: " + quotient);
     
    				x = 2;//when the user enters proper input, change x, so that the while condition below can terminate our do while loop.				
    			}
    			catch(NumberFormatException e){
    				//check if num1 is an integer
    				//check if num2 is an integer
    				//statement to catch a NumberFormatException?
     
    				System.out.println("Error. Invalid dividend or divisor. Please try again.");
    				continue;
     
    			}
    		}while(x==1);		
     
    	}//end of main
    }//end of class Test

    Lines 17 and 20 keep throwing the same error, "The method parseInt(String) in the type Integer is not applicable for the arguments (int)".

    I don't understand how the "e" parameter works in line 27's catch statement. Does it have to be "e" for a special reason? Would it still work if I used "fred" for the parameter instead?

    I'm unsure how to proceed making exception handlers. Am I just supposed to use a bunch of if statements? Do I need to use the continue statement in a do-while loop?
    why you using NextInt? and then Tryin to Parse Int to int value as Norm said .

    you should change your Varies to Strings , int x;
    then try to play with it

    and you can add e.getMessage() to catch block . in my opinion it seems better .

  4. #4
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    Default Re: My first functioning Try Catch program

    This is a joke. Why is NumberFormatException not doing anything:
    public class Test {
     
    	public static void main(String[] args){
    		Scanner input = new Scanner(System.in);
    		int userInput = 12;
    		boolean stayInLoop = true;
     
    		do{
    			try{				
    				System.out.println("Enter an integer between 0 and 10.");
    				userInput = input.nextInt();
    				//int parsedUserInput = Integer.parseInt(userInput);				
     
    				stayInLoop = false;//break;				
    			}
    			catch(NumberFormatException e){
    				if(userInput > 0 && userInput < 10){
    					System.out.println("Your integer is not between 0 and 10. Try again!"); 
    				}
    				else{
    					e.getMessage();
    				}
    				//statement to catch a datatype input mismatch by user?								
    				continue;				
    			}
    		}while(stayInLoop==true);
    		System.out.println("You're out of the loop after entering " + userInput);
     
    	}//end of main
    }//end of class Test

    Not only does my if statement not work:

    Enter an integer between 0 and 10.
    13
    You're out of the loop after entering 13


    But my program simply crashes instead of continuing the do while loop:
    Enter an integer between 0 and 10.
    12.3

    Exception in thread "main" java.util.InputMismatchException
    at java.util.Scanner.throwFor(Scanner.java:875)
    at java.util.Scanner.next(Scanner.java:1496)
    at java.util.Scanner.nextInt(Scanner.java:2128)
    at java.util.Scanner.nextInt(Scanner.java:2087)
    at sam.Test.main(Test.java:16)

    And here I thought that try catch mechanisms were supposed to correct the user, not crash the program.

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    Default Re: My first functioning Try Catch program

    That is not the exception you are catching.

    Regards,
    Jim

  6. #6
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    Default Re: My first functioning Try Catch program

    To see what method throws an exception, look at the API doc for that class.
    Also to see what exceptions a method throws.
    http://docs.oracle.com/javase/8/docs/api/index.html
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: My first functioning Try Catch program

    Quote Originally Posted by jim829 View Post
    That is not the exception you are catching.
    I still don't understand. Is Try Catch supposed to catch errors, or correct them? What can Try Catch do to correct errors that if statements cannot?

  8. #8
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    Default Re: My first functioning Try Catch program

    Read through the tutorial about exceptions: https://docs.oracle.com/javase/tutor...efinition.html
    If you don't understand my answer, don't ignore it, ask a question.

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