java - 如何限制用户在一定范围内输入数字？

Question

In Java, if you want to ask users, for example, to input numbers only between 1,000 and 100,000, the program would continue further. Otherwise, ask the user to input the number again in the given range.

Edit: Here, my program only tries to validate the input only once. How shall I make to ask the user to input until valid data(ie between 1000-100000) is entered

public static void main(String args[]) {

    Scanner sc = new Scanner(System.in);    
    System.out.print("Principal:");
    double principal = sc.nextDouble();

    if(principal<1000 || principal >100000) {
        System.out.println("enter principal again:");
        principal = sc.nextDouble();        
    }
}

Answer 1

You can use do-while loop here as below

public static void main(String []args){
    Scanner in = new Scanner(System.in);
    int result;
   do {
       System.out.println("Enter value bw 1-100");
       result = in.nextInt();
   } while(result < 0 || result > 100);

    System.out.println("correct "+ result);

}

Answer 2

import java.io.*;
import java.util.*;
import java.lang.*;
import java.math.*;

class Myclass {

    static boolean isInteger(double number){
        return Math.ceil(number) == Math.floor(number); 
    }
    public static void main(String args[]) {

        Scanner in = new Scanner(System.in);    
        double num;
        do{
            System.out.print("Enter a integer between 1000 and 100000 : ");
            num = in.nextDouble();
        }
        while((num < 1000 || num > 100000)||(!isInteger(num)));

        System.out.println("Validated input  : "+num);

    }
}

Hope this helps you