PatternSyntaxException类（java JDK源码记录）

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 18 
 19 package java.util.regex;
 20 
 21 /**
 22  * Unchecked exception thrown to indicate a syntax error in a
 23  * regular-expression pattern.
 24  *
 25  * @author  unascribed
 26  * @since 1.4
 27  * @spec JSR-51
 28  */
 29 
 30 public class PatternSyntaxException
 31     extends IllegalArgumentException
 32 {
 33     private static final long serialVersionUID = -3864639126226059218L;
 34 
 35     private final String desc;
 36     private final String pattern;
 37     private final int index;
 38 
 39     /**
 40      * Constructs a new instance of this class.
 41      *
 42      * @param  desc
 43      *         A description of the error
 44      *
 45      * @param  regex
 46      *         The erroneous pattern
 47      *
 48      * @param  index
 49      *         The approximate index in the pattern of the error,
 50      *         or {@code -1} if the index is not known
 51      */
 52     public PatternSyntaxException(String desc, String regex, int index) {
 53         this.desc = desc;
 54         this.pattern = regex;
 55         this.index = index;
 56     }
 57 
 58     /**
 59      * Retrieves the error index.
 60      *
 61      * @return  The approximate index in the pattern of the error,
 62      *         or {@code -1} if the index is not known
 63      */
 64     public int getIndex() {
 65         return index;
 66     }
 67 
 68     /**
 69      * Retrieves the description of the error.
 70      *
 71      * @return  The description of the error
 72      */
 73     public String getDescription() {
 74         return desc;
 75     }
 76 
 77     /**
 78      * Retrieves the erroneous regular-expression pattern.
 79      *
 80      * @return  The erroneous pattern
 81      */
 82     public String getPattern() {
 83         return pattern;
 84     }
 85 
 86     /**
 87      * Returns a multi-line string containing the description of the syntax
 88      * error and its index, the erroneous regular-expression pattern, and a
 89      * visual indication of the error index within the pattern.
 90      *
 91      * @return  The full detail message
 92      */
 93     public String getMessage() {
 94         StringBuilder sb = new StringBuilder();
 95         sb.append(desc);
 96         if (index >= 0) {
 97             sb.append(" near index ");
 98             sb.append(index);
 99         }
100         sb.append(System.lineSeparator());
101         sb.append(pattern);
102         if (index >= 0 && pattern != null && index < pattern.length()) {
103             sb.append(System.lineSeparator());
104             for (int i = 0; i < index; i++) sb.append(‘ ‘);
105             sb.append(‘^‘);
106         }
107         return sb.toString();
108     }
109 
110 }