Java regular expressions get matching and non-fetch matches

1  Packagetest1;2 3 ImportJava.util.regex.Matcher;4 ImportJava.util.regex.Pattern;5 6  Public classTestexp {7     /**8      * 9 * When using regular expressions, we often use () to enclose a part, called a sub-pattern. There are two cases of capturing and non-capturing in the sub-mode. Ten * Capturing means get match: One * means that the system will save all sub-pattern matching results behind the scenes for us to find or replace them. Use such as a back reference (applying the preceding matched substring after the expression); A * Non-capturing refers to a non-acquisition match: - * At this time the system does not save sub-pattern matching results, sub-pattern matching is only used as a restrictive condition, such as forward pre-check, reverse pre-check, negative forward pre-check, negative reverse pre-check and so on.  -      *  the * You can use non-fetch matches as criteria in Java to filter substrings. For example, to get "Hello World!" "Hello World" in the - *, note, do not exclamation mark. A non-fetching regular expression is used when the exclamation mark can be matched again. ("Hello World (? =!)" ) -      *  - * Use of back references in Java: + * "ABC def". Replacefirst ("(\\w+) \\s+ (\\w+)", "$ $ $");//result for DEF ABC - * "ABC def AAA BBB". ReplaceAll ("(\\w+) \\s+ (\\w+)", "$ $ $");//result is def ABC BBB AAA +      *  A * Use $x to replace character neutron strings.  at      *  -      * */ -      Public Static voidMain (string[] args) { -         /**The subscript for GroupCount starts at 0, which means that if you get a match, the value is 0 .*/ -         /**positive pre-check*/ -         /** in * Purpose: To find a substring in a meta-character that matches the "win" format, and the string immediately follows a "7" string.  -          *  to          * */ +         /* - * Pattern PTN = Pattern.compile ("Win (? =7)", pattern.unicode_case); the * Matcher m = ptn.matcher ("Win 7"); System.out.println ("GroupCount:" * * + m.groupcount ()); while (M.find ()) {System.out.println (M.group ());} $          */Panax Notoginseng         /**positive negative pre-check*/ -         /** the * Purpose: To find a substring in a meta-character that matches the "win" format, and the string is not followed by a "7" string.  +          *  A          * */ the         /* + * Pattern PTN = Pattern.compile ("Win (?! 7) ", pattern.unicode_case); - * Matcher m = ptn.matcher ("Win 8"); while (M.find ()) { $ * SYSTEM.OUT.PRINTLN (M.group ());} $          */ -         /**Reverse positive pre-check*/ -         /** the * Purpose: Finds the substring in the meta string that matches "win" and follows the string "7" in front of it. Win is obtained because 7 is not acquired.  -          * Wuyi          * */ the         /* - * Pattern PTN = Pattern.compile ("(? <=7) win", Pattern.unicode_case); Wu * Matcher m = ptn.matcher ("7win"); while (M.find ()) { - * SYSTEM.OUT.PRINTLN (M.group ());} About          */ $         /**Reverse negation pre-check*/ -         /** - * Purpose: Finds substrings in a meta string that match "win", and does not precede the string with "7".  -          *  A          */ +         /* the * Pattern PTN = Pattern.compile ("(? <!7) win", Pattern.unicode_case); - * Matcher m = ptn.matcher ("8win"); while (M.find ()) { $ * SYSTEM.OUT.PRINTLN (M.group ());} the          */ the     } the}

Java regular expressions get matching and non-fetch matches