src/java.base/share/classes/java/util/regex/Matcher.java

@@ -242,12 +242,15 @@
      Matcher(Pattern parent, CharSequence text) {
          this.parentPattern = parent;
          this.text = text;
  
          // Allocate state storage
-         int parentGroupCount = Math.max(parent.capturingGroupCount, 10);
-         groups = new int[parentGroupCount * 2];
+         if (parent.capturingGroupCount > 10) {
+             groups = new int[parent.capturingGroupCount * 2];
+         } else {
+             groups = new int[20];
+         }
          locals = new int[parent.localCount];
          localsPos = new IntHashSet[parent.localTCNCount];
  
          // Put fields into initial states
          reset();