feat: Function composition (#2954)

* feature: Implement Virtual Proxy pattern #2940

* feature: Implement Virtual Proxy pattern #2940

* feature: Implement Virtual Proxy pattern #2940

* feature: Implement Virtual Proxy pattern #2940

* feature: Implement Virtual Proxy pattern #2940

* feature: Implement Virtual Proxy pattern, tests added

* feature: Implement Virtual Proxy pattern, tests added

* feature: Implement Virtual Proxy pattern, tests added

* feature: Implement Virtual Proxy pattern, tests added

* feature: Implement Virtual Proxy pattern, tests added

* feature: Implement function composition pattern #2897

* task: isolate virtual proxy pattern

* task: isolate virtual proxy pattern

* refactoring: readme.md

function-composition/src/main/java/com/iluwatar/function/composition/App.java

@@ -0,0 +1,50 @@
+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 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.function.composition;
+
+import java.util.function.Function;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Main application class to demonstrate the use of function composition.
+ */
+public class App {
+
+  /**
+   * Main method to demonstrate function composition using FunctionComposer.
+   *
+   * @param args command line arguments (not used)
+   */
+  public static void main(String[] args) {
+    final var logger = LoggerFactory.getLogger(App.class);
+    Function<Integer, Integer> timesTwo = x -> x * 2;
+    Function<Integer, Integer> square = x -> x * x;
+
+    Function<Integer, Integer> composedFunction = FunctionComposer.composeFunctions(timesTwo, square);
+
+    int result = composedFunction.apply(3);
+    logger.info("Result of composing 'timesTwo' and 'square' functions applied to 3 is: " + result);
+  }
+}

function-composition/src/main/java/com/iluwatar/function/composition/FunctionComposer.java

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+/*
+ * This project is licensed under the MIT license. Module model-view-viewmodel is using ZK framework licensed under LGPL (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 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.function.composition;
+
+import java.util.function.Function;
+
+/**
+ * Class for composing functions using the Function Composition pattern.
+ * Provides a static method to compose two functions using the 'andThen' method.
+ */
+public class FunctionComposer {
+
+  /**
+   * Composes two functions where the output of the first function becomes
+   * the input of the second function.
+   *
+   * @param f1 the first function to apply
+   * @param f2 the second function to apply after the first
+   * @return a composed function that applies f1 and then f2
+   */
+  public static Function<Integer, Integer> composeFunctions(Function<Integer, Integer> f1, Function<Integer, Integer> f2) {
+    return f1.andThen(f2);
+  }
+}