Ignore [] brackets while capturing date with UNIFIED_DATE_TIMESTAMP (#444)

* Ignore [] brackets while capturing date with UNIFIED_DATE_TIMESTAMP

* Add test case for parsing GC log line with brackets

Author: srilakshmikanthanp

api/src/main/java/com/microsoft/gctoolkit/time/DateTimeStamp.java

@@ -65,7 +65,7 @@ private static double ageFromString(String doubleFormat) {
     private static final String TIME = INTEGER + DECIMAL_POINT + "\\d{3}";
 
     // Unified Tokens
-    private static final String DATE_TAG = "\\[" + DATE + "]";
+    private static final String DATE_TAG = "\\[(" + DATE + ")]";
     private static final String UPTIME_TAG = "\\[(" + TIME + ")s]";
 
     // Pre-unified tokens
@@ -81,15 +81,20 @@ private static double ageFromString(String doubleFormat) {
 
     public static DateTimeStamp fromGCLogLine(String line) {
         Matcher matcher;
-        int captureGroup = 2;
+        int dateCaptureGroup;
+        int ageCaptureGroup;
         if ( line.startsWith("[")) {
             matcher = UNIFIED_DATE_TIMESTAMP.matcher(line);
-            captureGroup = 3;
-        } else
+            dateCaptureGroup = 2;
+            ageCaptureGroup = 4;
+        } else {
             matcher = PREUNIFIED_DATE_TIMESTAMP.matcher(line);
+            dateCaptureGroup = 1;
+            ageCaptureGroup = 2;
+        }
 
         if ( matcher.find())
-            return new DateTimeStamp(dateFromString(matcher.group(1)), ageFromString(matcher.group(captureGroup)));
+            return new DateTimeStamp(dateFromString(matcher.group(dateCaptureGroup)), ageFromString(matcher.group(ageCaptureGroup)));
         else
             return EMPTY_DATE;
     }

api/src/test/java/com/microsoft/gctoolkit/time/DateTimeStampTest.java

@@ -483,4 +483,12 @@ void malformedDateTimeStampThrowsException() {
         assertThrows(IllegalStateException.class, () -> onlyDate.after(onlyTime));
     }
 
+    @Test 
+    void shouldParseGCLogLineWithBrackets() {
+        final String dateTimeString = "2025-05-08T11:07:55.681+0530";
+        final String gcLogLine = "[" + dateTimeString + "][gc,phases   ] GC(4)   Other: 0.2ms";
+        final DateTimeStamp dateTimeStamp = DateTimeStamp.fromGCLogLine(gcLogLine);
+        final ZonedDateTime expected = ZonedDateTime.from(formatter.parse(dateTimeString));
+        assertTrue(expected.isEqual(dateTimeStamp.getDateTime()));
+    }
 }