question: private final void add ( ThreadGroup g ) { synchronized ( this ) { if ( destroyed ) { throw new IllegalThreadStateException ( ) ; } if ( groups == null ) { groups = new ThreadGroup [ 4 ] ; } else if ( ngroups == groups . length ) { groups = Arrays . copyOf ( groups , ngroups * 2 ) ; } groups [ ngroups ] = g ; ngroups ++ ; } }
target:  Adds the specified Thread group to this group.