Question

Java如何判断输入的是字符还是数字？

Answer 1

1. 用JAVA自带的函数：

   public static boolean isNumeric(String str)

   for (int i = 0; i < str.length(); i++)

   System.out.println(str.charAt(i));

   if (!Character.isDigit(str.charAt(i)))

   return false;

2. 用正则表达式：

   首先要import java.util.regex.Pattern 和 java.util.regex.Matcher

   public boolean isNumeric(String str)

   Pattern pattern = Pattern.compile("[0-9]*");

   Matcher isNum = pattern.matcher(str);

   if( !isNum.matches() )

   return false;

3. 使用org.apache.commons.lang：

   org.apache.commons.lang.StringUtils;

   boolean isNunicodeDigits=StringUtils.isNumeric("aaa123456789");

   http://jakarta.apache.org/commons/lang/api-release/index.html下面的解释:

   isNumeric

   public static boolean isNumeric(String str)Checks if the String contains only unicode digits. A decimal point is not a unicode digit and returns false.

   null will return false. An empty String ("") will return true.

   StringUtils.isNumeric(null)   = false

   StringUtils.isNumeric("")     = true

   StringUtils.isNumeric("  ")   = false

   StringUtils.isNumeric("123")  = true

   StringUtils.isNumeric("12 3") = false

   StringUtils.isNumeric("ab2c") = false

   StringUtils.isNumeric("12-3") = false

   StringUtils.isNumeric("12.3") = false

   Parameters:
   

   str - the String to check, may be null

   Returns:

   true if only contains digits, and is non-null