DisplayAllocator(int n, StringCanvas t, Allocator a) {
   alloc_ = a;
   available = n;
   display_ = t;
   display_.setcolor(Color.cyan);
   display();
 }
 private void display() {
   display_.setString(
       "available= " + String.valueOf(available) + "  hired out= " + String.valueOf(hiredout));
 }