If you know the way merchandising machine works, you may divide its operation into primarily 4 states sold-out, idle, processing, and bought. Offered-out when the merchandising machine is simply began and never initialized, or all objects have already bought. Idle, when the merchandising machine is ready for the client to pick out an merchandise, Processing, as soon as the client has chosen merchandise and began inserting a coin, Offered when the client has paid the quantity.
All different strategies, which isn’t presupposed to be known as on these state, will do default operation, which will be both do nothing or throw an exception, as outlined in State summary class. Every State class retains a reference to Context, via which they’re related they usually additionally make state transition, I imply to vary the present state of Merchandising Machine.
Learn how to Design Merchandising Machine in Java utilizing State Design Sample – Instance
Right here is our full code instance of implementing Merchandising Machine utilizing State Design patterns in Java. When Merchandising Machine begins, it is initially on the SoldOut state then it strikes to Idle, as soon as it is initialized with a default variety of Objects and default variety of cash.
Merchandising Machine additionally supplies a technique that’s current in State summary class like choose(Merchandise i), insert(Coin c), refund(), and many others, however they’re delegated to the present state. When prospects choose merchandise by calling choose(Merchandise i) on Merchandising Machine, it delegates to currentState.choose(i), which is legitimate if Machine is within the Idle state after which it is going to transfer to Processing however will throw IllegalStateException if known as on different states.
- Coin.java
- Idle.java
- stock.java
- Merchandise.java
- NotSufficientChangeException.java
- Processing.java
- Offered.java
- SoldOut.java
- State.java
- VendingMachine.java
- VendingMachineTest.java
Coin.java
==========
public enum Coin {
PENNY(1), NICKLE(5), DIME(10), QUARTER(25);
personal int worth;
personal Coin(int worth){
this.worth = worth;
}
public int worth(){
return worth;
}
}
State.java
============
import java.util.Checklist;
public class State {
public void insert(Coin c){
throw new IllegalStateException();
}
public Checklist refund(){
throw new IllegalStateException();
}
public int select(Merchandise i){
throw new IllegalStateException();
}
public Merchandise dispense(){
throw new IllegalStateException();
}
public Checklist getChange() {
throw new IllegalStateException();
}
}
Idle.java
==========
public class Idle extends State{
personal VendingMachine machine;
public Idle(VendingMachine machine){
this.machine = machine;
}
@Override
public int select(Merchandise i) {
if(machine.itemInvertory.getCount(i) >= 1){
machine.currentItem = i;
machine.setState(new Processing(machine));
}else{
System.out.println(i + " bought out, Please strive one other drink");
}
return i.getPrice();
}
}
==========
import java.util.Checklist;
public class Offered extends State{
personal VendingMachine machine;
public Offered(VendingMachine machine){
this.machine = machine;
}
@Override
public Merchandise dispense(){
if(machine.itemInvertory.isEmpty()){
machine.setState(new SoldOut(machine));
}
machine.stability = machine.stability - machine.currentItem.getPrice();
machine.itemInvertory.take(machine.currentItem);
Merchandise bought = machine.currentItem;
machine.currentItem = null;
return bought;
}
@Override
public Checklist getChange(){
Checklist change = machine.getChange(machine.stability);
return change;
}
}
SoldOut.java
==============
public class SoldOut extends State{
personal VendingMachine machine;
public SoldOut(VendingMachine machine){
this.machine = machine;
}
}
Stock.java
===============
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
public class Stock {
personal Map retailer = new ConcurrentHashMap();
public int getCount(I merchandise){
Integer depend = retailer.get(merchandise);
return depend != null ? depend : 0;
}
public void add(I merchandise){
int depend = getCount(merchandise);
retailer.put(merchandise, ++depend);
}
public void take(I merchandise){
int depend = getCount(merchandise);
retailer.put(merchandise, --count);
}
public boolean isEmpty(){
return retailer.isEmpty();
}
boolean has(I i) {
return getCount(i) > 0;
}
}
Merchandise.java
==========
public enum Merchandise {
COKE(70), PEPSI(80), SPRITE(90);
personal int worth;
personal Merchandise(int worth){
this.worth = worth;
}
public int getPrice(){
return worth;
}
}
NotSufficientChangeException.java
==================================
public class NotSufficientChangeException extends RuntimeException {
personal String message;
public NotSufficientChangeException(String string) {
this.message = string;
}
@Override
public String getMessage() {
return message;
}
}
Processing.java
================
import java.util.Checklist;
public class Processing extends State{
personal VendingMachine machine;
public Processing(VendingMachine machine){
this.machine = machine;
}
@Override
public void insert(Coin c) {
machine.coinInvertory.add(c);
machine.stability = machine.stability + c.worth();
if (machine.stability >= machine.currentItem.getPrice()) {
if (machine.hasChange(machine.stability - machine.currentItem.getPrice())) {
machine.setState(new Offered(machine));
} else {
System.out.println("Machine haven't got
enough change, Please take refund");
}
}
}
@Override
public Checklist refund() {
machine.currentItem = null;
machine.setState(new Idle(machine));
Checklist change = machine.getChange(machine.stability);
machine.stability = 0;
return change;
}
}
VendingMachine.java
=====================
import java.util.ArrayList;
import java.util.Checklist;
public class VendingMachine {
personal State state;
Stock itemInvertory = new Stock();
Stock coinInvertory = new Stock();
Merchandise currentItem;
int stability;
public VendingMachine(){
state = new SoldOut(this);
initialize();
}
public void insert(Coin c){
state.insert(c);
}
public Checklist refund(){
return state.refund();
}
public int select(Merchandise i){
return state.select(i);
}
public Merchandise dispense(){
return state.dispense();
}
public void setState(State newState){
state = newState;
}
public Checklist getChange(){
return state.getChange();
}
personal void initialize() {
loadCoins();
loadItems();
this.state = new Idle(this);
}
personal void loadCoins(){
for(Coin c: Coin.values()){
coinInvertory.add(c);
coinInvertory.add(c);
coinInvertory.add(c);
coinInvertory.add(c);
coinInvertory.add(c);
}
}
personal void loadItems(){
for(Merchandise i: Merchandise.values()){
itemInvertory.add(i);
itemInvertory.add(i);
itemInvertory.add(i);
itemInvertory.add(i);
itemInvertory.add(i);
}
}
Checklist getChange(int stability) {
Checklist change = new ArrayList();
whereas(stability != 0){
if(stability >= Coin.QUARTER.worth() && coinInvertory.has(Coin.QUARTER)){
stability -= Coin.QUARTER.worth();
change.add(Coin.QUARTER); coinInvertory.take(Coin.QUARTER);
}else if(stability >= Coin.DIME.worth() && coinInvertory.has(Coin.DIME) ) {
stability -= Coin.DIME.worth();
change.add(Coin.DIME); coinInvertory.take(Coin.DIME);
}else if(stability >= Coin.NICKLE.worth() && coinInvertory.has(Coin.NICKLE)){
stability -= Coin.NICKLE.worth();
change.add(Coin.NICKLE); coinInvertory.take(Coin.NICKLE);
}else if(stability >= Coin.PENNY.worth() && coinInvertory.has(Coin.PENNY)) {
stability -= Coin.PENNY.worth();
change.add(Coin.PENNY); coinInvertory.take(Coin.PENNY);
}
if(coinInvertory.isEmpty() && stability >0){
throw new NotSufficientChangeException("Not Enough
Change for this buy");
}
}
return change;
}
boolean hasChange(int change) {
strive{
Checklist cash = getChange(change);
for(Coin c : cash){
coinInvertory.add(c);
}
}catch(NotSufficientChangeException ex){
return false;
}
return true;
}
}
VendingMachineTest.java
Right here is our take a look at program to check the code of VendingMachine which we’ve got carried out utilizing a State design sample. These exams will verify that whether or not state transitions work as anticipated or not. The code beneath makes use of JUnit annotation therefore you want JUnit 4.0 framework JAR information in your classpath. I’ve a few exams to purchase drinks with actual change and with extra change to see if our machine is working correctly or not.
In your follow, I’ve additionally added a few clean take a look at strategies like buyMultipleDrinks(), refund(), and buyAllDrinks(), you may implement these strategies to get some follow on writing JUnit take a look at circumstances
This UML diagram of State Design Sample may also provide help to undersand class construction and their relationship.
.
import java.util.Checklist;
import org.junit.Check;
import static org.junit.Assert.;
public class VendingMachineTest {
personal VendingMachine machine = new VendingMachine();
public VendingMachineTest(){
System.out.println("JUnit Framework calls
Constructor of take a look at class earlier than executing take a look at strategies");
}
@Check
public void buyDrinkWithExactAmount(){
int worth = machine.select(Merchandise.COKE);
assertEquals(70, worth);
assertEquals(Merchandise.COKE, machine.currentItem);
machine.insert(Coin.QUARTER);
machine.insert(Coin.QUARTER);
machine.insert(Coin.DIME);
machine.insert(Coin.DIME);
assertEquals(70, machine.stability);
assertEquals(7, (int) machine.coinInvertory.getCount(Coin.DIME));
assertEquals(7, (int) machine.coinInvertory.getCount(Coin.QUARTER));
Merchandise i = machine.dispense();
assertEquals(Merchandise.COKE, i);
assertEquals(4, (int) machine.itemInvertory.getCount(i));
Checklist change = machine.getChange();
assertTrue(change.isEmpty());
}
@Check
public void buyDrinkWithMoreAmount(){
int worth = machine.select(Merchandise.SPRITE);
assertEquals(90, worth);
assertEquals(Merchandise.SPRITE, machine.currentItem);
machine.insert(Coin.QUARTER);
machine.insert(Coin.QUARTER);
machine.insert(Coin.QUARTER);
machine.insert(Coin.QUARTER);
assertEquals(100, machine.stability);
assertEquals(9, (int) machine.coinInvertory.getCount(Coin.QUARTER));
Merchandise i = machine.dispense();
assertEquals(Merchandise.SPRITE, i);
assertEquals(4, machine.itemInvertory.getCount(i));
assertEquals(5, machine.itemInvertory.getCount(Merchandise.COKE));
Checklist change = machine.getChange();
assertEquals(1, change.measurement());
assertEquals(Coin.DIME, change.get(0));
assertEquals(4, machine.coinInvertory.getCount(Coin.DIME));
}
@Check
public void buyMultipleDrinks(){
}
@Check
public void refund(){
}
@Check
public void buyAllDrinks(){
}
}
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