docs: update function composition pattern

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

@@ -25,9 +25,10 @@
 package com.iluwatar.function.composition;
 
 import java.util.function.Function;
-import org.slf4j.LoggerFactory;
+import lombok.extern.slf4j.Slf4j;
 
 /** Main application class to demonstrate the use of function composition. */
+@Slf4j
 public class App {
 
   /**
@@ -36,7 +37,6 @@ public class App {
    * @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;
 
@@ -44,6 +44,6 @@ public class App {
         FunctionComposer.composeFunctions(timesTwo, square);
 
     int result = composedFunction.apply(3);
-    logger.info("Result of composing 'timesTwo' and 'square' functions applied to 3 is: " + result);
+    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

@@ -32,6 +32,8 @@ import java.util.function.Function;
  */
 public class FunctionComposer {
 
+  private FunctionComposer() {}
+
   /**
    * Composes two functions where the output of the first function becomes the input of the second
    * function.

function-composition/src/test/java/com/iluwatar/function/composition/FunctionComposerTest.java

@@ -30,7 +30,7 @@ import java.util.function.Function;
 import org.junit.jupiter.api.Test;
 
 /** Test class for FunctionComposer. */
-public class FunctionComposerTest {
+class FunctionComposerTest {
 
   /** Tests the composition of two functions. */
   @Test