Java determines the number in a string: whether it is a number, whether it contains numbers, how to intercept numbers

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JavaScript determines whether a character is a number, using the function: IsDigit ();

First, determine whether a string is a number

Package com.cmc.util;import Java.util.regex.matcher;import java.util.regex.Pattern; Public classDigitutil { Public Static voidMain (string[] args) {String str="123d"; System. out. println (IsDigit2 (str)); }        //determines whether a character is a number     Public Staticboolean isdigit (String strnum) {returnStrnum.matches ("[0-9]{1,}"); }        //determines whether a string is numeric     Public Staticboolean isDigit2 (String strnum) {pattern pattern= Pattern.compile ("[0-9]{1,}"); Matcher Matcher=Pattern.matcher ((charsequence) strnum); returnmatcher.matches (); }}

Second, determine whether the string contains a number

// determines whether a string contains a number     Public boolean hasdigit (String content) {        false;         = Pattern.compile (". *\\d+.*");         = p.matcher (content);         if (M.matches ()) {            true;        }         return flag;    }

Third, intercept the numbers in the string

Package com.cmc.util;import Java.util.regex.matcher;import java.util.regex.Pattern; Public classDigitutil { Public Static voidMain (string[] args) {String str="123dsd99"; System. out. println (Getnumbers (str)); ===> 123
SYSTEM.OUT.PRINTLN (Splitnotnumber (str)); ===> DSD}//intercept Number "reads the first contiguous string in a string, and does not contain subsequent discontinuous numbers"     Public Staticstring Getnumbers (string content) {pattern pattern= Pattern.compile ("\\d+"); Matcher Matcher=pattern.matcher (content);  while(Matcher.find ()) {returnMatcher.group (0); }          return ""; }            //Intercept non-digital    Public Staticstring Splitnotnumber (string content) {pattern pattern= Pattern.compile ("\\d+"); Matcher Matcher=pattern.matcher (content);  while(Matcher.find ()) {returnMatcher.group (0); }          return ""; }}

Iv. method of judging whether a string is a number

(i) using the Java Self-band function

     Public Static voidMain (string[] args) {String str="12399"; System. out. println (IsNumeric (str)); }        //determines whether a string is a number     Public Staticboolean isnumeric (String str) { for(inti = Str.length (); --i>=0;) {            if(!Character.isdigit (Str.charat (i))) {                return false; }        }        return true; }

(ii) using regular expressions

  public  static  void   main (string[] args) {String str  ="  123p99   "        ; System.  out     .println (IsNumeric2 (str));  public  static   Boolean isNumeric2 (String str) {pattern pattern  =pattern.compile (" [0-9]*   "         return   Pattern.matcher (str). matches (); }

(iii) using ASCII code

     Public Static voidMain (string[] args) {String str="12399"; System. out. println (ISNUMERIC3 (str)); }        //determines whether a string is a number     Public Staticboolean isNumeric3 (String str) { for(intI=str.length (); --i>=0;){            CharC=Str.charat (i); if(C < -|| C > $)                return false; }        return true; }

Java determines the number in a string: whether it is a number, whether it contains numbers, how to intercept numbers