CODEWITHSUNDEEP
javaexceptionjava.util.scanner
DezOnlyOne
DezOnlyOne

Reputation: 95

try catch for Scanner

I am using Scanner to get user input. If the user inputs a name, I add that to the ArrayList. If the user does not enter a name then I want to throw an exception, but I want to continue the loop that gets the answer. 

for(int i = 0; i < totalLanes; i++){
    runArr.add(this.addRacer());
}

public static String addRacer() throws NullPointerException{
    System.out.print("Enter a name for a racer: ");//Method uses try catch to catch a    NullPointerException.   
    Scanner sc = new Scanner(System.in);
    String rName = null;
    try {            
        if(!sc.nextLine().isEmpty()){
            rName = sc.nextLine();
        }else{
            throw new NullPointerException("name cannot be blank");
        }
    }

    catch (NullPointerException e) {
        System.out.println(e.toString());
        System.out.print("Enter a name for a racer: ");
        addRacer();
    }
    return rName;
}

Thanks in advance.

Upvotes: 0

Views: 3474

Answers (4)

Grzegorz G&#243;rkiewicz
Grzegorz G&#243;rkiewicz

Reputation: 4586

The problem is that you read input twice. I mean you have two calls of sc.nextLine() method in your code. Try this instead:

String rName = sc.nextLine();
try {
    if(rName.isEmpty()){
        throw new NullPointerException("Name cannot be blank.");
    }
}

Upvotes: 1

anuj mishra
anuj mishra

Reputation: 1

Don't call addRacer() function in catch. And also remove the line i have marked.Use if else condition for recursion.

catch (NullPointerException e) {
        System.out.println(e.toString());
        System.out.print("Enter a name for a racer: ");//remove this
        addRacer();//remove this
    }

Upvotes: 0

Youcef LAIDANI
Youcef LAIDANI

Reputation: 59950

You can use a do{}while() in your case, this can be better way :

Scanner sc = new Scanner(System.in);
String rName;

do {

    System.out.print("Enter a name for a racer: ");
    rName = sc.nextLine();
    try {
        if (rName.isEmpty()) {
            //throw and exception
            throw new NullPointerException("name cannot be blank");
        }
    } catch (NullPointerException e) {
        //print the exception
        System.out.println(e.getMessage());
    }

} while (rName.isEmpty());

return rName;

So you can't break your loop until the value in not empty.

Upvotes: 0

nhouser9
nhouser9

Reputation: 6780

You shouldn't throw an exception for that. Just use a while loop:

String rName = sc.nextLine();
while (rName.isEmpty()) {
    System.out.println("Name can't be blank. Try again.");
    rName = sc.nextLine();
}
return rName;

After that loop you are guaranteed to have a non-empty name in your variable, and you can use that name to add a new racer. You do not need recursion.

Upvotes: 0

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