Use default value if user skips input

user_15449378 0
Viewed 246

I want to ask the size of the array from the user. If the user does not enter the size and press the enter button, I want to use array size as 10 (default value). I am not able to do it. Here is my simple java code.

    System.out.print("Enter the size of Stack: ");
    int size = sc.nextInt();

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I am a beginner in java.

java
2 Answers

The problem is, that the sc.nextInt(); is waiting as long as it can find an int input.

A workaround for your problem could be to read the whole line and then try to parse this line to an int.

If the user-input is not an int (e.g. abcdefg or an empty String (only enter-button)), then the parsing will fail. Therefore in the catch block the default value is set.

E.g. it could look like this:

String sizeString = sc.nextLine();

int size;

try {
  size = Integer.parseInt(sizeString);
} catch (NumberFormatException e) {
  size = 10;
}
user_99015150

If you use nextLine() instead of nextInt() you can check if the enter key was pressed by comparing the input against an empty string.

        Scanner sc = new Scanner(System.in);
        
        System.out.print("Enter the size of Stack: ");
        // The replaceAll cleans the input by removing all non numeric characters
        String input = sc.nextLine().replaceAll("[^0-9]", "");;
        int size;
        
        // If the input is empty set size to 10 otherwise parse the string input as an integer
        if(input.equals("")){
            size = 10;
        }else{
            size = Integer.parseInt(input);
        }
        
        System.out.println(size);

Output:

Enter the size of Stack: 
10
user_155521520
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