fix Classpath 0.98 compatibility issues

classpath/java/lang/ThreadGroup.java

@@ -10,13 +10,20 @@
 
 package java.lang;
 
+import avian.Cell;
+
 public class ThreadGroup implements Thread.UncaughtExceptionHandler {
-  private final ThreadGroup parent;
+  final ThreadGroup parent; // package private for GNU Classpath compatibility
   private final String name;
+  private Cell<ThreadGroup> subgroups;
 
   public ThreadGroup(ThreadGroup parent, String name) {
     this.parent = parent;
     this.name = name;
+
+    synchronized (parent) {
+      parent.subgroups = new Cell(this, subgroups);
+    }
   }
 
   public ThreadGroup(String name) {
@@ -36,4 +43,75 @@ public class ThreadGroup implements Thread.UncaughtExceptionHandler {
       }
     }
   }
+
+  public ThreadGroup getParent() {
+    return parent;
+  }
+
+  public String getName() {
+    return name;
+  }
+
+  public int activeCount() {
+    int allCount = Thread.activeCount();
+    Thread[] all = new Thread[allCount];
+    allCount = Thread.enumerate(all);
+
+    int count = 0;
+    for (int i = 0; i < allCount; ++i) {
+      if (parentOf(all[i].getThreadGroup())) {
+        ++ count;
+      }
+    }
+
+    return count;
+  }
+
+  public int enumerate(Thread[] threads) {
+    return enumerate(threads, true);
+  }
+
+  public int enumerate(Thread[] threads, boolean recurse) {
+    int allCount = Thread.activeCount();
+    Thread[] all = new Thread[allCount];
+    allCount = Thread.enumerate(all);
+
+    int count = 0;
+    for (int i = 0; i < allCount && count < threads.length; ++i) {
+      Thread t = all[i];
+      ThreadGroup g = t.getThreadGroup();
+      if (g == this || (recurse && parentOf(g))) {
+        threads[count++] = t;
+      }
+    }
+
+    return count;
+  }  
+
+  public boolean parentOf(ThreadGroup g) {
+    for (; g != null; g = g.parent) {
+      if (g == this) {
+        return true;
+      }
+    }
+
+    return false;
+  }
+
+  public int enumerate(ThreadGroup[] groups, boolean recurse) {
+    return enumerate(groups, recurse, 0);
+  }
+
+  private int enumerate(ThreadGroup[] groups, boolean recurse, int count) {
+    for (Cell<ThreadGroup> c = subgroups; c != null && count < groups.length;
+         c = c.next)
+    {
+      ThreadGroup g = c.value;
+      groups[count++] = g;
+      if (recurse) {
+        count = g.enumerate(groups, true, count);
+      }
+    }
+    return count;
+  }
 }