如何在while循环中使用Java Scanner类使用OR条件？

Question

I am trying to use Scanner object sc to read in an integer from user's input and need to assess whether it's greater than 0. So I set the following OR conditions in the while() to check whether it's an empty line or the input number is less than 0. But the program does not take inputs after it encountered an invalid input. Any help is appreciated.

 Scanner sc = new Scanner(System.in);
 while (!sc.hasNextInt() || sc.nextInt() <= 0)
        {
            System.out.println("Invalid input\n the number needs to be greater than 0");
            sc.next();
        }
        int number = sc.nextInt(); 

Answer 1

The problem is probably that you're consuming the nextInt in the condition. You should read it into a variable:

package test;

import java.util.Scanner;

public class ScannerTest {
    public static void main(String[] arg) {
        Scanner sc = new Scanner(System.in);
        int input=-1;
        while(input<0){
            while (!sc.hasNextInt()) {
                if(sc.hasNext()){
                    String s = sc.next(); /* read things that are not Integers */
                    System.out.println("Invalid input:" + s);
                }
            }
            input = sc.nextInt();
            if(input<0){
                System.out.println("Please input a positive integer.");
            }
        }
        System.out.println("Valid input was "+input);
    }
}