Matcher Pattern

• public final class Matcher
  extends Object
  implements MatchResult

  An engine引擎 that performs执行  match operations操作  on a character sequence by interpreting解释  a Pattern.

  A matcher匹配器 is created from a pattern模式 by invoking调用  the pattern's matcher method. Once created, a matcher can be used to perform three different kinds of match operations:

  • The matches method attempts尝试  to match the entire整个的 input sequence against the pattern.

  • The lookingAt method attempts to match the input sequence, starting at the beginning, against the pattern.

  • The find method scans扫描  the input sequence looking for the next subsequence that matches the pattern.

  Each of these methods returns a boolean indicating表示  success or failure. More information about a successful match can be obtained获得  by querying the state of the matcher.

  A matcher finds matches in a subset子集  of its input called the region区域 . By default, the region contains all of the matcher's input. The region can be modified修改 via通过  theregion method and queried via theregionStart and regionEnd methods. The way that the region boundaries边界  interact with some pattern constructs构造  can be changed. SeeuseAnchoringBounds and useTransparentBounds for more details.

  This class also defines定义  methods for replacing matched subsequences with new strings whose contents can, if desired需要 , be computed计算 （new strings contents） from the match result. TheappendReplacement and appendTail methods can be used in tandem in order to collect the result into an existing 现有的 string buffer, or the more convenientreplaceAll method can be used to create a string in which every matching subsequence in the input sequence is replaced.

  The explicit显示state of a matcher includes the start and end indices索引 of the most recent 最近的successful match. It also includes the start and end indices of the input subsequence captured捕获  by eachcapturing group in the pattern as well as a total count of such subsequences. As a convenience方便 , methods are also provided for returning these captured subsequences in string form形式.

  The explicit state of a matcher is initially最初 undefined; attempting尝试  to query any part of it before a successful match will cause anIllegalStateException to be thrown. The explicit state of a matcher is recomputed重新计算 by every match operation.

  The implicit 隐式 state of a matcher includes the input character sequence as well as the append position, which is initially zero and is updated by the appendReplacement method.

  A matcher may be reset explicitly by invoking its reset() method or, if a new input sequence is desired需要, its reset(CharSequence) method. Resetting a matcher discards 放弃its explicit state information and sets the append position to zero.

  Instances of this class are not safe for use by multiple concurrent并发 threads.  

  
  

  • public final class Pattern
    extends Object
    implements Serializable

    A compiled编译 representation of a regular expression.

    A regular expression, specified as a string, must first be compiled into an instance of this class. The resulting得到  pattern can then be used to create aMatcher object that can match arbitrary任意 character sequences against the regular expression. All of the state involved in performing a match resides in the matcher, so many matchers can share the same pattern.

    A typical典型  invocation调用 sequence is thus

     Pattern p = Pattern.compile("a*b");
     Matcher m = p.matcher("aaaaab");
     boolean b = m.matches();

    A matches method is defined by this class as a convenience for when a regular expression is used just once. This method compiles an expression and matches an input sequence against it in a single invocation. The statement

     boolean b = Pattern.matches("a*b", "aaaaab");

    is equivalent to the three statements above, though for repeated matches it is less efficient since it does not allow the compiled pattern to be reused.

    Instances of this class are immutable and are safe for use by multiple concurrent threads. Instances of theMatcher class are not safe for such use