I have four classes Customer, Store and Item and Online.
I am using ‘LinkedList’ to move around classes.
I added items at the Customer class.
When I want to check whether the item under exists or not under Online class.
Because you cannot check at the Customer.
I use the hasItem().It’s failing constantly.
When I say that, I mean even though I type “001A:GTA”, the item is store in the data and it’s not working. it keep returning null.
Can someone explain to me? I really appreciate it. I am a complete begineer.
Item Class
public class Item {
private String code;
private String name;
public Item(String code, String name) {
this.code = code;
this.name = name;
}
public boolean hasItem(String code, String name){
return code.equals(this.code) && name.equals(this.name);
}
@Override
public String toString() {
return name + " : " + code;
}
}
Store class
public class Store {
private LinkedList<Item> items = new LinkedList<Item>();
public Store(String name, String number) {
this.name = name;
this.number = number;
}
public void addItem(String code, String name){
items.add(new Item(this, code, name);
}
public LinkedList<Item> viewItem(){
for(int j = 0 ; j < items.size(); j++)
System.out.println(items.get(j))
return null;
}
}
Customer
public class Customer {
private LinkedList<Store> stores = new LinkedList<Store>();
public Customer() {
stores.add(new Store("Game", "1"));
stores.add(new Store("Grocery", "2"));
stores.get(0).addItem("001A", "GTA");
stores.get(0).addItem("001B", "GOD OF WARS");
stores.get(0).addItem("001C", "THE LAST OF US");
stores.get(1).addItem("002A", "Sandwich");
stores.get(1).addItem("002B", "Cup Noodle");
stores.get(1).addItem("002C", "Ice Cream");
}
public static void main(String args[]) {
new Customer().view();
}
public void view() {
System.out.println(stores.get(0).viewItem());
}
}
Online Class
class Online{
private LinkedList<Item> items = new LinkedList<Item>();
private String name ;
private String number;
public Online(String name, String number){
this.name = name;
this.number = number;
}
public static void main(String args[]){
new Customer(“John”, “012”).view();
}
private void view(){
Item item = item(“001A:GTA”);
if(item != null)
System.out.println(“Found”);
else
System.out.println(“Not found”):
}
public Item item(String item){
String[] temp = item.split(":");
String code = temp[0];
String name = temp[1];
for(Item item: items)
if(item.hasItem(code, name))
return item;
return null;
}
}
}
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Answer
Override Object::equals
Do it as follows:
import java.util.LinkedList;
import java.util.Objects;
class Item {
private String code, name;
public Item(String code, String name) {
this.code = code;
this.name = name;
}
public String getName() {
return name;
}
@Override
public String toString() {
return name + " : " + code;
}
@Override
public int hashCode() {
return Objects.hash(name, code);
}
@Override
public boolean equals(Object obj) {
Item item = (Item) obj;
return name.equals(item.name) && code.equals(item.code);
}
}
class Store {
private LinkedList<Item> items = new LinkedList<Item>();
private String name, number;
public Store(String name, String number) {
this.name = name;
this.number = number;
}
public String getName() {
return name;
}
public void addItem(String code, String name) {
items.add(new Item(code, name));
}
public LinkedList<Item> findItems() {
return items;
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
for (Item item : items) {
sb.append(item.toString()).append(System.lineSeparator());
}
return sb.toString();
}
public void viewStore() {
System.out.println(name + " " + number);
}
/**
* Searches the item in the store using the search string
*
* @param The string combining the code and name in the format "code:name:"
* @return Returns the matching Item. If the item is not found, null is returned
*/
public Item findItem(String strItem) {
String[] data = strItem.split(":");
if (data.length < 2) {
return null;
}
Item searchItem = new Item(data[0], data[1]);
for (Item item : items) {
if (item.equals(searchItem)) {
return item;
}
}
return null;
}
/**
* Searches the item in the store using the name of the item
*
* @param The name of the item
* @return Returns the matching Item. If the item is not found, null is returned
*/
public Item findItemByName(String itemName) {
for (Item item : items) {
if (item.getName().equals(itemName)) {
return item;
}
}
return null;
}
}
class Customer {
private LinkedList<Store> stores = new LinkedList<Store>();
public Customer() {
stores.add(new Store("Game", "1"));
stores.add(new Store("Grocery", "2"));
stores.get(0).addItem("001A", "GTA");
stores.get(0).addItem("001B", "GOD OF WARS");
stores.get(0).addItem("001C", "THE LAST OF US");
stores.get(1).addItem("002A", "Sandwich");
stores.get(1).addItem("002B", "Cup Noodle");
stores.get(1).addItem("002C", "Ice Cream");
}
public LinkedList<Store> getStores() {
return stores;
}
public void viewStore() {
for (Store store : stores)
store.viewStore();
}
public void viewItems() {
for (Store store : stores) {
for (Item item : store.findItems()) {
System.out.println(item);
}
}
}
/**
* Searches the item in all the stores related to the customer using the search
* string
*
* @param The string combining the code and name in the format "code:name:"
* @return Returns the matching Item. If the item is not found, null is returned
*/
public Item findItem(String strItem) {
String[] data = strItem.split(":");
if (data.length < 2) {
return null;
}
Item searchItem = new Item(data[0], data[1]);
for (Store store : stores) {
for (Item item : store.findItems()) {
if (item.equals(searchItem)) {
return item;
}
}
}
return null;
}
/**
* Searches the item in all the stores related to the customer using the name of
* the item
*
* @param The name of the item
* @return Returns the matching Item. If the item is not found, null is returned
*/
public Item findItemByName(String itemName) {
for (Store store : stores) {
for (Item item : store.findItems()) {
if (item.getName().equals(itemName)) {
return item;
}
}
}
return null;
}
}
public class Online {
public static void main(String[] args) {
Item item;
String strItem, itemName;
Customer customer = new Customer();
// Test searching the item using the search string in a particular store e.g.
// first store of customer
Store store = customer.getStores().get(0);
System.out.println("Searching item using search string in store, " + store.getName());
strItem = "001A:GTA";
item = store.findItem(strItem);
if (item == null) {
System.out.println("Not found -> " + strItem);
} else {
System.out.println("Found -> " + item);
}
strItem = "002A:Sandwich";
item = store.findItem(strItem);
if (item == null) {
System.out.println("Not found -> " + strItem);
} else {
System.out.println("Found -> " + item);
}
System.out.println();
// Test searching the item using the search string in all the stores related to
// the customer
System.out.println("Searching item using search string in all the stores related to the customer");
strItem = "001A:GTA";
item = customer.findItem(strItem);
if (item == null) {
System.out.println("Not found -> " + strItem);
} else {
System.out.println("Found -> " + item);
}
strItem = "002A:Sandwich";
item = customer.findItem(strItem);
if (item == null) {
System.out.println("Not found -> " + strItem);
} else {
System.out.println("Found -> " + item);
}
strItem = "ABC:XYZ";
item = customer.findItem(strItem);
if (item == null) {
System.out.println("Not found -> " + strItem);
} else {
System.out.println("Found -> " + item);
}
System.out.println();
// Test searching the item using name of the item in a particular store e.g.
// first store of customer
store = customer.getStores().get(0);
System.out.println("Searching item using name of the item in store, " + store.getName());
itemName = "GTA";
item = store.findItemByName(itemName);
if (item == null) {
System.out.println("Not found -> " + strItem);
} else {
System.out.println("Found -> " + item);
}
itemName = "Sandwich";
item = store.findItemByName(itemName);
if (item == null) {
System.out.println("Not found -> " + itemName);
} else {
System.out.println("Found -> " + item);
}
System.out.println();
// Test searching the item using the name of the item in all the stores related
// to the customer
System.out.println("Searching item using name of the item in all the stores related to the customer");
itemName = "GTA";
item = customer.findItemByName(itemName);
if (item == null) {
System.out.println("Not found -> " + itemName);
} else {
System.out.println("Found -> " + item);
}
itemName = "Sandwich";
item = customer.findItemByName(itemName);
if (item == null) {
System.out.println("Not found -> " + itemName);
} else {
System.out.println("Found -> " + item);
}
itemName = "XYZ";
item = customer.findItemByName(itemName);
if (item == null) {
System.out.println("Not found -> " + itemName);
} else {
System.out.println("Found -> " + item);
}
}
}
Output:
Searching item using search string in store, Game Found -> GTA : 001A Not found -> 002A:Sandwich Searching item using search string in all the stores related to the customer Found -> GTA : 001A Found -> Sandwich : 002A Not found -> ABC:XYZ Searching item using name of the item in store, Game Found -> GTA : 001A Not found -> Sandwich Searching item using name of the item in all the stores related to the customer Found -> GTA : 001A Found -> Sandwich : 002A Not found -> XYZ
Note that it doesn’t sound good for the class, Item to have a method called, hasItem. It gives an impression as if class, Item is a container class. Also, it is always a recommended practice to override Object::equals and Object::hashCode in a class. It makes your code clean (as you can see in the code given above) and helps you write logic in an easy manner; especially when you are dealing with collections.