【java】实现一个简单的正则：判断一个字符串是否全由数字组成

 1 package 正则;
 2 
 3 public class TestIsNum {
 4     public static void main(String[] args) {
 5         String s1="abc";
 6         String s2="987652345678009876543211234567890";
 7         String s3="a5678";
 8         String s4="23456789j";
 9         System.out.println(isNums(s1));
10         System.out.println(isNums(s2));
11         System.out.println(isNums(s3));
12         System.out.println(isNums(s4));
13         System.out.println(isNumsGoodMethod(s1));
14         System.out.println(isNumsGoodMethod(s2));
15         System.out.println(isNumsGoodMethod(s3));
16         System.out.println(isNumsGoodMethod(s4));
17         
18     }
19     public static boolean isNums(String arr){        
20         char[] charArray=arr.toCharArray();
21         char[] nums={'0','1','2','3','4','5','6','7','8','9'};
22         for(int i=0;i<charArray.length;i++){
23             for(int j=0;j<nums.length;j++){                
24                 if(charArray[i]==nums[j]){
25                     break;
26                 }
27                 if(j==nums.length-1){                    
28                     return false;
29                 }                    
30             }
31         }
32         return true;
33     }
34     public static boolean isNumsGoodMethod(String arr){
35         char[] charArray=arr.toCharArray();
36         for(char c:charArray){
37             if(c>'9'||c<'0')
38                 return false;
39         }
40         return true;
41     }
42 }