Add a new regex to filter

Author: DamonFool

test/lib/jdk/test/lib/containers/cgroup/MetricsTesterCgroupV2.java

@@ -122,9 +122,7 @@ private long getLongValueEntryFromFile(String file, String metric) {
         Path filePath = Paths.get(UNIFIED.getPath(), file);
         try {
             String strVal = Files.lines(filePath)
-                                 .filter(l -> l.startsWith(metric))
-                                 .filter(l -> l.split("\\s+")[0].equals(metric))
-                                 .collect(Collectors.joining());
+                                 .filter(l -> l.matches("^" + metric + "\\s+.*")).collect(Collectors.joining());
             if (strVal.isEmpty()) {
                 // sometimes the match for the metric does not exist, e.g. cpu.stat's nr_periods iff the controller
                 // is not enabled