Code Refactoring 11
One of you guys sent me a request to explain the chapter in Refactoring to Patterns titled Encapsulate Composite with Builder. We will build a table structure (composite) using the Builder design pattern.
I’ll expand the capabilities of the code from this great book to allow us to more easily traverse the tree structure. This will allow us to add children, siblings and item information using a HashMap. This is a beautiful refactoring. All of the code can be found below to help you learn it.
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Code From the Video
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
public class Item{
// I'm using a HashMap to store key value pairs
private HashMap<String, String> itemInfoHM;
private String itemName = "";
// Will store children of this Item in a tree
private ArrayList<Item> children = new ArrayList<Item>();
public String getItemName() { return itemName; }
public void setItemName(String itemName) { this.itemName = itemName; }
public Item(String itemName) {
super();
setItemName(itemName);
// Create Item HashMap that stores Item info
itemInfoHM = new HashMap<String, String>(20);
}
// Used to add children nodes
public void add(Item childNode) { children.add(childNode); }
public void addItemInformation(String infoName, String info){
itemInfoHM.put(infoName, info);
}
public String getItemInformation(String infoName){
return itemInfoHM.get(infoName);
}
public String toString() {
String itemInformation = "\n" + itemName + " ";
// If Item info is available get it
if (!itemInfoHM.isEmpty()){
itemInformation += displayProductInfo();
}
Iterator<Item> it = children.iterator();
// Attach all children for this Item
while (it.hasNext()) {
Item node = (Item)it.next();
itemInformation += node.toString();
}
return itemInformation;
}
public String displayProductInfo() {
String productInfo = "";
// Cycle through every key, value pair and return them
// entrySet() returns a Set that contains the Map entries
for (Map.Entry<String, String> entry : itemInfoHM.entrySet()) {
productInfo += entry.getKey() + ": " + entry.getValue() + " ";
}
return productInfo;
}
public static void main(String[] args){
// Create an Item that stores all others, or the Root
ItemBuilder products = new ItemBuilder("Products");
// Add children and their info
products.addChild("Produce");
products.addChild("Orange");
products.addItemInformation("Price", "$1.00");
products.addItemInformation("In Stock", "100");
// Add siblings
products.addSibling("Apple");
products.addSibling("Grapes");
// Change the current Item to the Root of the tree
products.editThisItem("Products");
products.addChild("Cereal");
products.addChild("Special K");
products.addItemInformation("Price", "$3.68");
products.addSibling("Raisin Bran");
products.addItemInformation("Price", "$3.78");
products.editThisItem("Apple");
products.addItemInformation("Price", "$.25");
products.addSibling("Peach");
products.editThisItem("Cereal");
products.addChild("Fiber One");
products.addItemInformation("Price", "$4.00");
products.displayAllItems();
// Print information on just the Cereal Item and its children
System.out.println("\n" + products.getItemByName("Cereal"));
}
}
class ItemBuilder {
// Holds all of the Items created
ArrayList<Item> items = new ArrayList<Item>();
// Stores the root and parent Item objects for the
// current Item you are working with so you can
// add siblings and children based on location in
// the tree structure
private Item root;
private Item current;
private Item parent;
public ItemBuilder(String rootName) {
root = new Item(rootName);
addItemToArrayList(root);
current = root;
parent = root;
// Store the parent for the Item object
root.addItemInformation("Parent", parent.getItemName());
}
// Allows me to store Item information
public void addItemInformation(String name, String value) {
current.addItemInformation(name, value);
}
// Adds a Child Item to the current parent Item
public void addChild(String child) {
Item childNode = new Item(child);
addItemToArrayList(childNode);
current.add(childNode);
parent = current;
current = childNode;
// Store the parent for the Item object
childNode.addItemInformation("Parent", parent.getItemName());
}
// Adds a sibling Item to the current Item stored in current
public void addSibling(String sibling) {
Item siblingNode = new Item(sibling);
addItemToArrayList(siblingNode);
// Adding a child node to the parent Item
parent.add(siblingNode);
current = siblingNode;
// Store the parent for the Item object
siblingNode.addItemInformation("Parent", parent.getItemName());
}
// Adds Item objects to ArrayList
public void addItemToArrayList(Item newItem){
items.add(newItem);
}
public String toString() {
return root.toString();
}
public void displayAllItems(){
for(Item item : items){
System.out.println(item.getItemName() + ": " + item.displayProductInfo());
}
}
// Changes the Current Item object that is being used
public void editThisItem(String itemName){
for(Item item : items){
if(item.getItemName().equals(itemName)){
current = item;
// Gets the name of the stored parent object
// and passes it so that parent can be set
// as the parent in the ItemBuilder
setItemsParent(current.getItemInformation("Parent"));
}
}
}
// Sets the Parent Item for ItemBuilder
public void setItemsParent(String parentItem){
for(Item item : items){
if(item.getItemName().equals(parentItem)){
parent = item;
}
}
}
// Returns the Item based on the name passed into the method
public Item getItemByName(String itemToGet){
Item itemToReturn = null;
for(Item item : items){
if(item.getItemName().equals(itemToGet)){
itemToReturn = item;
}
}
return itemToReturn;
}
}
Where is the code ??? =(
Sorry about that. I uploaded it now. I uploaded this very late last night
Very good code, nice way to do a tree with composition using the builder pattern to actually build the tree. Thx a lot!
You’re very welcome
Many more refactorings are in the works
hey darek,
do you have any plan of making some short video tutorials for how to improve performance of java applications or something like that?
Yes I’ll cover that in the future. For the most part I write pretty code all of the time though
all right
Hello Derek!
Nice tutorial! Had 2 questions on this subject. Would it be good to combine the Builder and Composite pattern in this kind of cases?
What if you try to achieve the same thing, keep track of the tree, with just the Composite pattern (and i guess some “tree-track-holder-class”), is there a reason to choose for the Builder pattern instead?
Always feel free to combine patterns in any way that makes your code easier to understand. There is never a reason to not do something if it makes for understandable code
Hey Derek! Love love the tutorials!
I am trying to make a program that excess a database and using AI changes the data and stores it back.
Would this pattern work well with accessing databases?
Thanks!
Roger
Hey Roger, Thank you very much
You could use this if you aren’t planning on having a ton of data. A HashMap isn’t very efficient if you have a large number of elements.
Thank you! I appreciate the input!
You’re very welcome