user input check int only

Question

I am trying to have my user input not crash my program by restricting what the user can input such as:

1. only being an int
2. being between 1-30

<

Answer 1

do:
get number from user
if non integer format is entered{
number = -1;}
while: 1 < number < 30

Answer 2

See dasblinkenlight's awnser with the NumberFormatException catch. I was thinking of doing that. This also works too:

You need to combine the two loops like so:

while(true) {
if(!sc.hasNextInt) {
System.out.println("Only Integers!");
continue;
}
choose = sc.nextInt();
if(choose <= 0) {
System.out.println("The number you entered was too small.");
continue;
} else if(choose > 30) {
System.out.println("The number you entered was too large.\nMax: 30");
continue;
}
break;
}
sc.close();

Answer 3

You need to combine the two loops, so that both checks happen every time the end-user enters something new:

for(;;) {
    if(!sc.hasNextInt() ) { 
        System.out.println("only integers!: "); 
        sc.next(); // discard
        continue;
    } 
    choose=sc.nextInt();
    if( choose<=0 || choose>30)
    {
        System.out.print("no, 1-30: ");
        continue;
    }
    break;
}

After the loop exits, choose is a number between 1 and 30, inclusive.

Answer 4

    String choose = "";
    System.out.println("Test if input is an integer. Type 'quit' to exit.");
    System.out.print("Type an integer: ");
    Scanner sc=new Scanner(System.in);

    choose = sc.nextLine();

    while (!(choose.equalsIgnoreCase("quit"))) {
        int d = 0;
        try {
            d = Integer.parseInt(choose);

            if (!(d > 0 && d < 31)) {
                System.out.println("Being between 1-30");
            } else {
                System.out.println("Input is an integer.");
            }
        } catch (NumberFormatException nfe) {
            System.out.println("Enter only int");
        }

        System.out.print("Type an integer to test again or 'quit' to exit: ");
        sc = new Scanner(System.in);
        choose = sc.nextLine();
    }

    sc.close();
    System.out.print("Program ends.");