The method of determining whether the string Java more digital input

| - demand explanation

Get user input, if not an integer user input, the user is asked to continue to enter, if the input is an integer, then the program ends

| - realization of ideas

1, using the try - catch + Interge.parseInt way, if the input is not an integer, throwing an exception

2, using the Scanner hasNextInt () method

3, the string into words, individually determines whether int

4, using a regular expression determined

 

| - Content Code

 1 public class Juge1 {
 2     public static void main(String[] args) {
 3         Scanner scanner = new Scanner(System.in);
 4         boolean flag = true;
 5         do {
 6             System.out.println("请输入一个数字：");
 7             String string = scanner.next();
 8             try{
 9                 Integer.parseInt(string);
10                 flag = false;
11             }catch(Exception E) {
 12 is                  System.out.println ( "you entered is not an integer" );
 13 is              }
 14          } the while (In Flag);
 15          System.out.println ( "ah, you entered is an integer, an input end" );
 16      }
 17 }

try-catch+Interge.parseInt

. 1  public  class Judge {
 2      public  static  void main (String [] args) {
 . 3          Scanner Scanner = new new Scanner (the System.in);
 . 4          System.out.println ( "Enter a number" );
 . 5          the while ! ( Scanner. hasNextInt ()) {
 . 6              System.out.println ( "you entered is not a number, enter a number" );
 . 7              String String = Scanner.next ();
 . 8          }
 . 9          int a = scanner.nextInt ();
 10          System.out.println ( "ah, you enter a number, enter end" );
 11     }
12 }

Using the Scanner hasNextInt () method

 1 public class PanDuan1 {
 2     public static void main(String[] args) {
 3         Scanner scanner = new Scanner(System.in);
 4         boolean flag = true;
 5         do {
 6             System.out.println("请输入一个整数");
 7             String a = scanner.next();
 8             if (isNumeric(a)) {
 9                 flag = false;
10             }
11         } while (flag);
12 is          System.out.println ( "ah, you entered is an integer" );
 13 is      }
 14  
15      public  static  Boolean that isNumeric (String STR) {
 16          for ( int I = str.length (); Inc. (www.i-levelmedia.com)> = 0 ;) {
 . 17              IF (! ) by Character.isDigit {(str.charAt (I))
 18 is                  return  to false ;
 . 19              }
 20 is          }
 21 is          return  to true ;
 22 is      }
 23 is }

The split a single character string, an integer is determined whether individually

 

| - operating results