如何在 Java 中同时检查下一个输入是否为 > 和 < 时检查下一个输入是否为整数？

Question

There's two things I'm needing help with. Loop issue 1) I have to initialize this variable outside of the loop, which makes the loop fail if the user inputs a string. Is there a way around that? Basically, if I set N to anything then the do-while loop just immediately reads it after getting out of the

import java.util.Scanner;

/**
 * Calculates sum between given number
 */

public class PrintSum {

    public static void main(String[] args) {

        int N = 0;
        String word;

        boolean okay;
        Scanner scan = new Scanner(System.in);
        System.out.print("Please enter a number from 1-100: ");
        do {
            if (scan.hasNextInt()) {
                N = scan.nextInt();
            } else {
                okay = false;
                word = scan.next();
                System.err.print(word + " is an invalid input. Try again. ");
            }
            if (N > 100 || N < 1) {
                okay = false;
                System.err.print("Invalid Input. Try again. ");
            } else { 
                okay = true;
            }
        } while (!okay);
        loop(N, 0);
    }

    public static void loop(int P, int total) {
        while (P >= 1) {
            total = total + P;
            P--;
        }

        System.out.println(total);

    }
}

If not, then the issue becomes, how do I solve this? I thing that I need to be able to say

if (scan.hasNextInt() || ??? > 100 || ??? < 1) {
                okay = false;
                word = scan.next();
                System.err.print(word + " is an invalid input. Try again. ");
            } else {
                okay = true;
            }

What do I put in the??? to make this work? I think I just don't know enough syntax.

Thank you!

Answer 1

Why don't you try this?

do {
            if (scan.hasNextInt()) {
                N = scan.nextInt();
            } else {
                okay = false;
                word = scan.next();
                System.err.print(word + " is an invalid input. Try again. ");
                continue;
            }
            if (N > 100 || N < 1) {
                okay = false;
                System.err.print("Invalid Input. Try again. ");
                continue;
            } else { 
                okay = true;
            }
        } while (!okay);

break is used to end the loop as soon as the user enters the invalid character(condition of the else clause), so the loop doesn't fail.
Looking at your edited question, continue is what you are looking for if you might want to allow the user to enter another value after entering the invalid value.
Use break or continue based on requirement. More on breaks and continue. Your second approach can be solved as follows:

if (scan.hasNextInt()){
    N = scan.nextInt();
    if (N > 100 || N < 1) {
        System.err.print("Invalid input. Try again. ");
    }
    //perform some operation with the input
}
else{
    System.err.print("Invalid Input. Try again. ");
}