Java怎样判定输入是否为数字？

String number = 输入的值; for(int i = 0; i < number.length; i++) { String numberChar = number.substring(i,i+1); if((numberChar >= "a" && numberChar <= "z") || numberChar == 符号) // 等于符号的情况不知道 { System.out.println("输入的是数字"); } else { if((int)numberChar >= 0 && (int)numberChar <= 9) { System.out.println("输入的是数字"); } } }

import java.util.Scanner; /** * @author Sun@XMU * */ public class StarText { public static void main(String[] args) { Scanner input = new Scanner(System.in); try{ int a = Integer.parseInt(input.next()); System.out.println(a); }catch(NumberFormatException e){ System.err.println("Error ,please Enter a Int number"); } } }