#564: Collection Pipeline pattern

collection-pipeline/src/main/java/com/iluwatar/collectionpipeline/FunctionalProgramming.java

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+/**
+ * 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.
+ */
+package com.iluwatar.collectionpipeline;
+
+import java.util.Comparator;
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * Iterating and sorting with a collection pipeline
+ * 
+ * <p>In functional programming, it's common to sequence complex operations through
+ * a series of smaller modular functions or operations. The series is called a
+ * composition of functions, or a function composition. When a collection of
+ * data flows through a function composition, it becomes a collection pipeline.
+ * Function Composition and Collection Pipeline are two design patterns
+ * frequently used in functional-style programming.
+ * 
+ * <p>Instead of passing a lambda expression to the map method, we passed the
+ * method reference Car::getModel. Likewise, instead of passing the lambda
+ * expression car -> car.getYear() to the comparing method, we passed the method
+ * reference Car::getYear. Method references are short, concise, and expressive.
+ * It is best to use them wherever possible.
+ * 
+ */
+public class FunctionalProgramming {
+  private FunctionalProgramming() {
+  }
+
+  /**
+   * Method to get models using for collection pipeline.
+   * 
+   * @param cars {@link List} of {@link Car} to be used for filtering
+   * @return {@link List} of {@link String} representing models built after year 2000
+   */
+  public static List<String> getModelsAfter2000UsingPipeline(List<Car> cars) {
+    return cars.stream().filter(car -> car.getYear() > 2000)
+      .sorted(Comparator.comparing(Car::getYear))
+      .map(Car::getModel).collect(Collectors.toList());
+  }
+}