What are some methods of determining whether a string is a number in string--java?

A method for determining whether a string is a number in Ava: 1. The Java-brought function public static Boolean isnumeric (String str) {for (int i = 0; i < str.length (); i++) {S   Ystem.out.println (Str.charat (i)); if (!   Character.isdigit (Str.charat (i))) {return false; }} return true; }2. Use regular Expressions first to import Java.util.regex.Pattern and Java.util.regex.Matcherpublic boolean isnumeric (String str) {Pattern Patt    Ern = Pattern.compile ("[0-9]*");   Matcher isnum = Pattern.matcher (str);    if (!isnum.matches ()) {return false; } return true; }3. Using Org.apache.commons.langorg.apache.commons.lang.stringutils;boolean isnunicodedigits=stringutils.isnumeric ( "aaa123456789"); http://jakarta.apache.org/commons/lang/api-release/index.html the following explanation: Isnumericpublic static Boolean isnumeric (String str) Checks If the string contains only Unicode digits. A decimal point was not a Unicode digit and returns False.null would return false. An empty String ("") would return true. Stringutils.isnumeric (NULL) = False Stringutils.isnumeric ("") = True StringutilS.isnumeric ("") = False Stringutils.isnumeric ("123") = True Stringutils.isnumeric ("3") = False Stringutils.isnumer  IC ("AB2C") = False Stringutils.isnumeric ("12-3") = False Stringutils.isnumeric ("12.3") = False parameters:str-the String To check, could be null returns:true if only contains digits, and is non-null above three ways, the second way is more flexible. The first to third way can only check the number without the minus sign "-", that is, enter a negative-199, the output will be false, and the second way you can modify the regular expression to implement the check negative, the regular expression is modified to "^-?" [0-9]+], modified to "-?" [0-9]+.? [0-9]+] to match all numbers.

What are some methods of determining whether a string is a number in string--java?