Work on iluwatar#381, added draft implementation of service stub pattern. Doing this to help @jdoetricksy get the hang of abstractions

Author: npathai

service-stub/pom.xml

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+<?xml version="1.0"?>
+<!--
+
+    The MIT License
+    Copyright (c) 2014 Ilkka Seppälä
+
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation files (the "Software"), to deal
+    in the Software without restriction, including without limitation the rights
+    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+    copies of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included in
+    all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+    THE SOFTWARE.
+
+-->
+<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>com.iluwatar</groupId>
+    <artifactId>java-design-patterns</artifactId>
+    <version>1.13.0-SNAPSHOT</version>
+  </parent>
+  <artifactId>service-stub</artifactId>
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-core</artifactId>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>com.yahoofinance-api</groupId>
+      <artifactId>YahooFinanceAPI</artifactId>
+      <version>3.1.0</version>
+    </dependency>
+  </dependencies>
+</project>

service-stub/src/main/java/com/iluwatar/servicestub/service/App.java

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+package com.iluwatar.servicestub.service;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+public class App {
+
+  public static void main(String[] args) throws Exception {
+    ExecutorService executor = Executors.newSingleThreadExecutor();
+
+    try {
+      YahooStockService service = new YahooStockService();
+
+      Portfolio portfolio = new Portfolio("iluwatar");
+      BuyAtCurrentPriceCommand googleCurrentPriceBuy = new BuyAtCurrentPriceCommand(service, portfolio, 
+          new Stock("GOOG", "Google"), 100);
+      googleCurrentPriceBuy.execute();
+
+      BuyAtCurrentPriceCommand yahooCurrentPriceBuy = new BuyAtCurrentPriceCommand(service, portfolio, 
+          new Stock("YHOO", "Yahoo"), 100);
+      yahooCurrentPriceBuy.execute();
+
+      BuyAtLimitPriceCommand yahooLimitPriceBuy = new BuyAtLimitPriceCommand(service, portfolio, 
+          new Stock("YHOO", "Yahoo"), 100,service.getQuote(new Stock("YHOO", "Yahoo")).getCurrentPrice(),
+          executor);
+
+      yahooLimitPriceBuy.execute().get();
+
+      System.out.println(portfolio);
+    } finally {
+      executor.shutdownNow();
+    }
+  }
+}

service-stub/src/main/java/com/iluwatar/servicestub/service/BuyAtCurrentPriceCommand.java

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+package com.iluwatar.servicestub.service;
+
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Future;
+
+public class BuyAtCurrentPriceCommand {
+
+  private StockService service;
+  private Portfolio portfolio;
+  private Stock stock;
+  private int quantity;
+
+  public BuyAtCurrentPriceCommand(StockService service, Portfolio portfolio, Stock stock, int quantity) {
+    this.service = service;
+    this.portfolio = portfolio;
+    this.stock = stock;
+    this.quantity = quantity;
+  }
+  
+  public Future<Void> execute() {
+    try {
+      StockQuote stockQuote = service.getQuote(stock);
+      portfolio.add(stock, quantity, stockQuote.getCurrentPrice());
+      return CompletableFuture.completedFuture(null);
+    } catch (Exception e) {
+      CompletableFuture<Void> future = new CompletableFuture<>();
+      future.completeExceptionally(e);
+      return future;
+    }    
+  }
+}

service-stub/src/main/java/com/iluwatar/servicestub/service/BuyAtLimitPriceCommand.java

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+package com.iluwatar.servicestub.service;
+
+import java.math.BigDecimal;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executor;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+
+public class BuyAtLimitPriceCommand {
+  private StockService service;
+  private Portfolio portfolio;
+  private Stock stock;
+  private int quantity;
+  private BigDecimal priceLimit;
+  private Executor executor;
+
+  public BuyAtLimitPriceCommand(StockService service, Portfolio portfolio, Stock stock, 
+      int quantity, BigDecimal priceLimit,
+      Executor executor) {
+    this.service = service;
+    this.portfolio = portfolio;
+    this.stock = stock;
+    this.quantity = quantity;
+    this.priceLimit = priceLimit;
+    this.executor = executor;
+  }
+
+  public Future<Void> execute() {
+    CompletableFuture<Void> future = new CompletableFuture<>();
+    executor.execute(() -> {
+      try {
+        while (true) {
+          StockQuote stockQuote = service.getQuote(stock);
+          
+          if (stockQuote.getCurrentPrice().compareTo(priceLimit) <= 0) {
+            portfolio.add(stock, quantity, stockQuote.getCurrentPrice());
+            future.complete(null);
+            break;
+          } else {
+            Thread.sleep(TimeUnit.SECONDS.toMillis(1));
+          }
+        }
+        
+      } catch (Exception e) {
+        future.completeExceptionally(e);
+      }    
+      
+    });
+    return future;
+  }
+}

service-stub/src/main/java/com/iluwatar/servicestub/service/Portfolio.java

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+package com.iluwatar.servicestub.service;
+
+import java.math.BigDecimal;
+import java.util.HashMap;
+import java.util.Map;
+
+public class Portfolio {
+
+  private final String username;
+  private final Map<Stock, StockInformation> stockToStockInformation = new HashMap<>();
+  private BigDecimal totalAssets;
+  
+  public Portfolio(String username) {
+    this.username = username;
+    this.totalAssets = new BigDecimal(0);
+  }
+
+  public void add(Stock stock, int quantity, BigDecimal price) {
+    StockInformation stockInformation = stockToStockInformation.get(stock);
+    if (stockInformation == null) {
+      stockInformation = new StockInformation(stock, price, quantity);
+      stockToStockInformation.put(stock, stockInformation);
+    } else {
+      stockInformation.add(quantity, price);
+    }
+    totalAssets = totalAssets.add(price.multiply(new BigDecimal(quantity)));
+  }
+  
+  @Override
+  public String toString() {
+    
+    StringBuilder stringBuilder = new StringBuilder();
+    stringBuilder.append(String.format("User: %s | Total assets worth: %f%n", username, totalAssets.floatValue()));
+    for (StockInformation stockInformation : stockToStockInformation.values()) {
+      stringBuilder.append(stockInformation.toString()).append("\n");
+    }
+    
+    return stringBuilder.toString();
+  }
+
+  public StockInformation get(Stock stock) {
+    return stockToStockInformation.get(stock);
+  }
+}

service-stub/src/main/java/com/iluwatar/servicestub/service/SellCommand.java

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+package com.iluwatar.servicestub.service;
+
+public class SellCommand {
+
+  
+}

service-stub/src/main/java/com/iluwatar/servicestub/service/Stock.java

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+package com.iluwatar.servicestub.service;
+
+public class Stock {
+
+  private final String symbol;
+  private final String name;
+
+  public Stock(String symbol, String name) {
+    this.symbol = symbol;
+    this.name = name;
+  }
+
+  public String getSymbol() {
+    return symbol;
+  }
+
+  public String getName() {
+    return name;
+  }
+
+  @Override
+  public int hashCode() {
+    final int prime = 31;
+    int result = 1;
+    result = prime * result + ((symbol == null) ? 0 : symbol.hashCode());
+    return result;
+  }
+
+  @Override
+  public boolean equals(Object obj) {
+    if (this == obj)
+      return true;
+    if (obj == null)
+      return false;
+    if (getClass() != obj.getClass())
+      return false;
+    Stock other = (Stock) obj;
+    if (symbol == null) {
+      if (other.symbol != null)
+        return false;
+    } else if (!symbol.equals(other.symbol))
+      return false;
+    return true;
+  }
+  
+  
+  
+}

service-stub/src/main/java/com/iluwatar/servicestub/service/StockInformation.java

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+package com.iluwatar.servicestub.service;
+
+import java.math.BigDecimal;
+
+public class StockInformation {
+
+  private final Stock stock;
+  private BigDecimal totalStockPrice;
+  private int quantity;
+  
+  
+  public StockInformation(Stock stock, BigDecimal buyPrice, int quantity) {
+    this.stock = stock;
+    this.totalStockPrice = buyPrice.multiply(new BigDecimal(quantity));
+    this.quantity = quantity;
+  }
+  
+  public Stock getStock() {
+    return stock;
+  }
+  
+  public BigDecimal getAverageStockPrice() {
+    return totalStockPrice.divide(new BigDecimal(quantity));
+  }
+  
+  public int getQuantity() {
+    return quantity;
+  }
+
+  public void add(int quantity, BigDecimal price) {
+    this.quantity += quantity;
+    this.totalStockPrice = totalStockPrice.add(price.multiply(new BigDecimal(quantity)));
+  } 
+  
+  @Override
+  public String toString() {
+    return String.format("Stock: %s | Quantity: %d | Avg.Price: %f", stock.getName(), quantity, getAverageStockPrice().floatValue());
+  }
+}

service-stub/src/main/java/com/iluwatar/servicestub/service/StockQuote.java

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+package com.iluwatar.servicestub.service;
+
+import java.math.BigDecimal;
+
+public class StockQuote {
+
+  private final BigDecimal currentPrice;
+
+  public StockQuote(BigDecimal currentPrice) {
+    this.currentPrice = currentPrice;
+  }
+
+
+  public BigDecimal getCurrentPrice() {
+    return currentPrice;
+  }
+  
+  @Override
+  public String toString() {
+    return String.format("Current trading price: %f", currentPrice.floatValue());
+  }
+  
+}

service-stub/src/main/java/com/iluwatar/servicestub/service/StockService.java

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+package com.iluwatar.servicestub.service;
+
+public interface StockService {
+
+    StockQuote getQuote(Stock stock) throws Exception;
+}

service-stub/src/main/java/com/iluwatar/servicestub/service/StockServiceStub.java

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+package com.iluwatar.servicestub.service;
+
+import java.math.BigDecimal;
+
+public class StockServiceStub implements StockService {
+  private StockQuote quote;
+
+  public StockServiceStub(BigDecimal quotePrice) {
+    this.quote = new StockQuote(quotePrice);
+  }
+
+  @Override
+  public StockQuote getQuote(Stock stock) throws Exception {
+    return quote;
+  }
+  
+  public void setQuotePrice(BigDecimal quotePrice) {
+    this.quote = new StockQuote(quotePrice);
+  }
+}

service-stub/src/main/java/com/iluwatar/servicestub/service/YahooStockService.java

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+package com.iluwatar.servicestub.service;
+
+import yahoofinance.Stock;
+import yahoofinance.YahooFinance;
+
+public class YahooStockService implements StockService {
+
+  @Override
+  public StockQuote getQuote(com.iluwatar.servicestub.service.Stock stock) throws Exception {
+    Stock yahooStock = YahooFinance.get(stock.getSymbol());
+    return new StockQuote(yahooStock.getQuote().getPrice());
+  }
+
+}