code: @Override
  	@SuppressWarnings({"checkstyle:npathcomplexity", "checkstyle:magicnumber"})
  	public void clear() {
  		if (this.child1 != null) {
  			final N child = this.child1;
  			setChildAt(0, null);
  			child.clear();
  		}
  		if (this.child2 != null) {
  			final N child = this.child2;
  			setChildAt(1, null);
  			child.clear();
  		}
  		if (this.child3 != null) {
  			final N child = this.child3;
  			setChildAt(2, null);
  			child.clear();
  		}
  		if (this.child4 != null) {
  			final N child = this.child4;
  			setChildAt(3, null);
  			child.clear();
  		}
  		if (this.child5 != null) {
  			final N child = this.child5;
  			setChildAt(4, null);
  			child.clear();
  		}
  		if (this.child6 != null) {
  			final N child = this.child6;
  			setChildAt(5, null);
  			child.clear();
  		}
  		if (this.child7 != null) {
  			final N child = this.child7;
  			setChildAt(6, null);
  			child.clear();
  		}
  		if (this.child8 != null) {
  			final N child = this.child8;
  			setChildAt(7, null);
  			child.clear();
  		}
  		removeAllUserData();
  	}
docs: Clear the tree.
  
  <p>Caution: this method also destroyes the
  links between the child nodes inside the tree.
  If you want to unlink the first-level
  child node with
  this node but leave the rest of the tree
  unchanged, please call <code>setChildAt(i,null)</code>.