How do I loop back to the start of the TRY statement?

Question

How do I make it loop back to the start of the FOR loop again? I had try searching the answers. Use of continue don't seems to work for me.

try{

    for (int i = 0; i < Array1.length; i++){
        System.out.println("enter Values ");

        Scanner input = new Scanner(System.in);
        Array1[i]= input.nextInt();
    }
}//try
catch (InputMismatchException e) 
{
    System.out.println("pls enter integers only ");

}//catch

How do I go about continuing the process again? For example

Enter Values 5 enter Values 1 enter Values g pls enter integers only ->> error exception is over here

After this error show, how am I able to continue the enter values process without retyping from value 1?

Do you mean you want to start the whole loop again (with i as 0), or continue with the next iteration of the loop? — Jon Skeet, Oct 18 '13 at 05:49

Kayaman · Accepted Answer · 2013-10-18T05:55:48.423

3

You'll have to put the try/catch inside the for loop (and decrease i in the catch block, so all the indexes will be filled).

Since people seem to be confused about the basics here, why not have the whole fricking code:

Scanner input = new Scanner(System.in);
System.out.println("Enter integer values: ");
for (int i = 0; i < Array1.length; i++){
    try {
        Array1[i]= input.nextInt();
    } catch (InputMismatchException e) {
        System.out.println("Please enter integers only");
        i--;
    }
}
// Now your Array1 is filled with ints

edited Oct 18 '13 at 05:55

answered Oct 18 '13 at 05:49

Kayaman

72,141
5
83
121

2

Absolutely redundant, `try- catch` inside for loop, No ? – Suresh Atta Oct 18 '13 at 05:50
1

Nothing redundant about it. That's where the exception is thrown (from nextInt()). If you decrease i in the catch block, the for loop won't terminate (and the index won't increase) until you've inserted valid integers. – Kayaman Oct 18 '13 at 05:53
@sᴜʀᴇsʜᴀᴛᴛᴀ it is not. – Luiggi Mendoza Oct 18 '13 at 05:53
Maybe leave a comment why it is a damn good idea to not initialize a Scanner inside the for loop, but put initialization before (as you have correctly done). Good thing to educate the OP a bit more. BTW +1 from me. – Matthias Oct 18 '13 at 06:01

Lorenzo Barbagli · Answer 2 · 2013-10-19T22:18:12.820

You say how to roll back if an exception occours? Can't you insert the try/catch statement inside the for cycle?

Scanner input = null;

for (int i = 0; i < Array1.length; i++){
    System.out.println("enter Values ");

    input = new Scanner(System.in);
    try {
        Array1[i]= input.nextInt();
    } catch (InputMismatchException e) {
        System.out.println("pls enter integers only ");
    }
}

CODE EDITED: best programming use is to declare variables outside loops

Trying · Answer 3 · 2013-10-18T05:59:25.863

it will start afresh if any exception occurs.

    for(int i=0;i<a.length;i++){
        try{
            System.out.println("enter Values ");
            Scanner input = new Scanner(System.in);
            a[i]=input.nextInt();
        }
        catch(InputMismatchException e){
            System.out.println(e.getMessage());
            i=-1;
        }
    }

below will just try to fetch the value where it fired exception:

for(int i=0;i<a.length;i++){
            try{
                System.out.println("enter Values ");
                Scanner input = new Scanner(System.in);
                a[i]=input.nextInt();
            }
            catch(InputMismatchException e){
                System.out.println(e.getMessage());
                i--;
            }
        }

Almost there. Why don't you look at my solution. – Kayaman Oct 18 '13 at 05:57 — Kayaman, Oct 18 '13 at 05:57

score 1 · Answer 4 · answered Oct 18 '13 at 06:12

Try using the following code.

try{
            for (int i = 0; i < Array1.length; i++){
                System.out.println("enter Values ");

                Scanner input = new Scanner(System.in);
                Array1[i]= input.nextInt();
                if(i==Array1.length-1) i=0;
            }
        }//try
        catch (InputMismatchException e) 
        {
            System.out.println("pls enter integers only ");

        }

which will consistently execute the same loop. Is this what you want?

what i want is to loop back to tell user to enter an integer again.without forgetting the values the user had type before the error occur — Gerald Tan, Oct 18 '13 at 06:18

Se Won Jang · Answer 5 · 2013-10-18T06:24:25.190

0

If you want to start the entire process again upon catching the exception,

boolean isValid = false;

while(isValid == false) {
try{

    for (int i = 0; i < Array1.length; i++){
        System.out.println("enter Values ");
        Scanner input = new Scanner(System.in);
        Array1[i]= input.nextInt();
    }
    isValid = true;
}//try
catch (InputMismatchException e) 
{
    System.out.println("pls enter integers only ");

}//catch
}

edited Oct 18 '13 at 06:24

answered Oct 18 '13 at 05:51

Se Won Jang

773
1
5
12

Does not compile. 1st line `False` needs be `false`. And `while(isValide == false)` should be `while(isValid == false)` – Matthias Oct 18 '13 at 06:04
all java keywords are in small case, **False** should be **false** – SpringLearner Oct 18 '13 at 06:11

score 0 · Answer 6 · answered Oct 18 '13 at 06:23

try{
for (int i = 0; i < Array1.length; i++){    
System.out.println("enter Values ");
Scanner input = new Scanner(System.in);    
    Array1[i]= input.nextInt();
}
} 
catch (InputMismatchException e) {System.out.println("pls enter integers only ");
i = 0;
continue;
}

Hope it helps.

How do I loop back to the start of the TRY statement?

6 Answers6