[ Java 代碼範本 ] 判斷字串是否為數字

參考自 這裡
- 用JAVA自帶的函數

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1. public  static  boolean  isNumeric(String str){   
2.   for  ( int  i  =  0 ; i  <  str.length(); i ++ ){   
3.    System.out.println(str.charAt(i));   
4.    if  ( ! Character.isDigit( str.charAt(i))){   
5.     return  false ;   
6.    }   
7.   }   
8.   return  true ;   
9. }  

- 用正則表達式

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1. package test.stlib;  
2.   
3. import java.util.regex.Matcher;  
4. import java.util.regex.Pattern;  
5.   
6. public class JudgeStrAsNum {  
7.     public static void main(String[] args) {  
8.         String intStrArry[] = {"1.0", "-1.2", "0.3", "123.0", "abc", "a123", ".12"};  
9.         Pattern ptn = Pattern.compile("^-?[0-9]+(\\.[0-9]+)?$");  
10.         Matcher mth = null;  
11.         for(String intStr:intStrArry)  
12.         {  
13.             mth = ptn.matcher(intStr);  
14.             if(mth.find())  
15.             {  
16.                 System.out.printf("\t[Info] %s is a number.\n", intStr);  
17.             }  
18.             else  
19.             {  
20.                 System.out.printf("\t[Info] %s is not a number.\n", intStr);  
21.             }  
22.                   
23.         }  
24.     }  
25. }  

執行結果 :

[Info] 1.0 is a number.
[Info] -1.2 is a number.
[Info] 0.3 is a number.
[Info] 123.0 is a number.
[Info] abc is not a number.
[Info] a123 is not a number.
[Info] .12 is not a number.

This message was edited 3 times. Last update was at 16/08/2012 10:10:45