Can a local variable be used out of a method?

问题

I've got stuck in a problem about local variables.

The following is not my original code but I use a simple example to present my question:

import java.util.Scanner;
public static void main(String[] args) {
    Scanner userScan=new Scanner(System.in);    
    do{
        int input1=userScan.nextInt();
    }while(input1>10);
}

My purpose is to let a user type in an integer which is in my intended range. If the typed number does not meet the rule, I hope the user can type again until it does. However, the "input1" is a local variable, so it will not be valid in the expression of while. But I do not want the user to re-type the integer again. Using only one variable would be better. Does anyone have advices about it or other ways which can implement this idea? Thank you!

回答1:

    public static void main(String[] args) 
   {
        Scanner userScan=new Scanner(System.in);    
        int input1;
        do{
            input1=userScan.nextInt();
        }while(input1>10);
    }

just declare input1 outside of the scope of do while loop

回答2:

Why don't you just do this? :D Delcare the input1 outside the do...while loop, then it can be used in while statement.

import java.util.Scanner;
    public static void main(String[] args) {
        Scanner userScan=new Scanner(System.in);  
        int input1 = 0;
        do{
            input1=userScan.nextInt();
        }while(input1>10);
    }

回答3:

The problem is with your input1 variable scope i.e., the scope of your input1 variable is limited to do while block (i.e., { } code), so just declare the variable outside the loop.

int input1 = 0;//scope is now wider, not just limited to the loop
do {
   input1=userScan.nextInt();
} while(input1>10);

来源：https://stackoverflow.com/questions/43016946/can-a-local-variable-be-used-out-of-a-method