(RPM) Java six ways to determine if a string variable is a number

1. Using Regular Expressionsfirst, import Java.util.regex.Pattern and Java.util.regex.Matcher

/*** Use regular expressions to determine if a string is a number *@paramSTR *@return     */     Public Booleanisnumeric (String str) {pattern pattern= Pattern.compile ("[0-9]*"); Matcher Isnum=Pattern.matcher (str); if( !isnum.matches ()) {               return false; }           return true; }

2. Functions with Java

 Public Static Boolean isnumeric (String str) {   for (int i = 0; i < str.length (); i++) {System.out.print　　　　ln (Str.charat (i));  if (! 　　　Character.isdigit (Str.charat (i))) {    　　　　returnfalse;   }}  returntrue;

3. Using Org.apache.commons.lang

org.apache.commons.lang.StringUtils;BooleanIsnunicodedigits=stringutils.isnumeric ("aaa123456789"); http://jakarta.apache.org/commons/lang/api-release/index.html The following explanation: Public Static BooleanIsNumeric (String str) ChecksifThe String contains only Unicode digits. A decimal point was not a Unicode digit and returnsfalse.NULLWouldreturn false. An empty String ("") wouldreturn true. Stringutils.isnumeric (NULL)   =falseStringutils.isnumeric ("")     =trueStringutils.isnumeric (" ")   =falseStringutils.isnumeric ("123") =trueStringutils.isnumeric ("12 3") =falseStringutils.isnumeric ("AB2C") =falseStringutils.isnumeric ("12-3") =falseStringutils.isnumeric ("12.3") =false

4. Judging ASCII code value

 Public Static Boolean isNumeric0 (String str)
{
　　 for (int i=str.length ();--i>=0;)
{   　　int chr=str.charat (i);   　　 if (chr<48 | | chr>57)    　　　　 return false ;
}  returntrue;

5. Determine whether the characters in Str are 0-9

 Public Static Boolean isNumeric3 (String str)
{  final String number = "0123456789";    for (int i = 0; i < number.length; i + +)
  {
if (Number.indexof (Str.charat (i)) = =-1)
     {  
        returnfalse;       }    }     return true ;}

6. Capturing NumberFormatException anomalies

 Public Static Boolean isNumeric00 (String str)
{  try{   integer.parseint (str);   　　 return true ;  } Catch (NumberFormatException e)
  {System.out.println ("Exception: \" "+ str +" \ "is not a number/integer ...");  returnfalse;  }}

(GO) Java to determine whether a string variable is a number of six methods summary