【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

package 正则;

public class TestIsNum {
    public static void main(String[] args) {
        String s1="abc";
        String s2="987652345678009876543211234567890";
        String s3="a5678";
        String s4="23456789j";
        System.out.println(isNums(s1));
        System.out.println(isNums(s2));
        System.out.println(isNums(s3));
        System.out.println(isNums(s4));
        System.out.println(isNumsGoodMethod(s1));
        System.out.println(isNumsGoodMethod(s2));
        System.out.println(isNumsGoodMethod(s3));
        System.out.println(isNumsGoodMethod(s4));
        
    }
    public static boolean isNums(String arr){        
        char[] charArray=arr.toCharArray();
        char[] nums={'0','1','2','3','4','5','6','7','8','9'};
        for(int i=0;i<charArray.length;i++){
            for(int j=0;j<nums.length;j++){                
                if(charArray[i]==nums[j]){
                    break;
                }
                if(j==nums.length-1){                    
                    return false;
                }                    
            }
        }
        return true;
    }
    public static boolean isNumsGoodMethod(String arr){
        char[] charArray=arr.toCharArray();
        for(char c:charArray){
            if(c>'9'||c<'0')
                return false;
        }
        return true;
    }
}