Merge pull request #32 from craft-coder/java8-comparators

Creates an example of how to use the Comparator Interface from Java 1.2 that is now a Functional Interface closed #8

Author: alexandregama

java8-comparators/.gitignore

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+/target/
+build/
+.classpath
+.project
+.settings

java8-comparators/README.md

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+# java8-guides-tutorials
+Java 8 - Guides and Tutorias

java8-comparators/pom.xml

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+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+<modelVersion>4.0.0</modelVersion>
+
+<groupId>com.craftcoder.java8</groupId>
+<artifactId>java8-comparators</artifactId>
+<version>0.0.1-SNAPSHOT</version>
+<packaging>jar</packaging>
+
+<name>java8-comparators</name>
+<url>http://maven.apache.org</url>
+
+<properties>
+<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+</properties>
+
+<dependencies>
+<!-- TESTING DEPENDENCIES -->
+<dependency>
+<groupId>org.hamcrest</groupId>
+<artifactId>hamcrest-all</artifactId>
+<version>1.3</version>
+</dependency>
+
+<dependency>
+<groupId>junit</groupId>
+<artifactId>junit</artifactId>
+<version>4.12</version>
+<scope>test</scope>
+</dependency>
+ <!-- TESTING DEPENDENCIES -->
+
+</dependencies>
+
+<build>
+<plugins>
+<plugin>
+<groupId>org.apache.maven.plugins</groupId>
+<artifactId>maven-eclipse-plugin</artifactId>
+<configuration>
+<downloadSources>true</downloadSources>
+<downloadJavadocs>true</downloadJavadocs>
+</configuration>
+</plugin>
+</plugins>
+</build>
+
+</project>

java8-comparators/src/java/test/com/craftcoder/java8/defaultmethod/DefaultMethodTest.java

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+package com.craftcoder.java8.defaultmethod;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalTo;
+
+import org.junit.Ignore;
+import org.junit.Test;
+
+public class DefaultMethodTest {
+
+/**
+ * In this example, we don't need to use the default method send() from PaymentService interface 
+ */
+@Ignore
+@Test
+public void shouldRetrieveTheDefaultFees() throws Exception {
+PaymentService service = new PayPalPaymentService();
+
+double fees = service.retrieveDefaultFees();
+
+assertThat(fees, equalTo(10.9));
+}
+
+@Test
+public void shouldInvokeTheDefaultMethodFromPaymentService() throws Exception {
+PaymentService paymentService = new PayPalPaymentService();
+
+double valueSent = paymentService.send(20);
+
+assertThat(valueSent, equalTo(20.0));
+}
+
+}
+
+
+interface PaymentService {
+
+double retrieveDefaultFees();
+
+default double send(double value) {
+System.out.println("Sending the value: " + value);
+
+return value;
+}
+
+}
+
+class PayPalPaymentService implements PaymentService {
+
+@Override
+public double retrieveDefaultFees() {
+return 10.9;
+}
+
+}

java8-comparators/src/test/java/com/craftcoder/java8/comparator/ComparatorFunctionalInterfaceTest.java

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+package com.craftcoder.java8.comparator;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.greaterThan;
+import static org.hamcrest.Matchers.lessThan;
+
+import java.util.Comparator;
+
+import org.junit.Test;
+
+public class ComparatorFunctionalInterfaceTest {
+
+@Test
+public void shouldCompareTwoGuidesByUsingComparator() throws Exception {
+CraftCoderGuide mockito = new CraftCoderGuide("Mockito");
+CraftCoderGuide java = new CraftCoderGuide("Java 8");
+
+Comparator<CraftCoderGuide> comparator = new Comparator<CraftCoderGuide>() {
+
+@Override
+public int compare(CraftCoderGuide first, CraftCoderGuide second) {
+return first.getName().compareTo(second.getName());
+}
+};
+
+int compared = comparator.compare(mockito, java);
+
+assertThat(compared, greaterThan(0));
+}
+
+@Test
+public void shouldCompareTwoGuidesByUsingComparatorWithLambdaExpression() throws Exception {
+CraftCoderGuide mockito = new CraftCoderGuide("Mockito");
+CraftCoderGuide java = new CraftCoderGuide("Java 8");
+
+Comparator<CraftCoderGuide> comparator = (first, second) -> first.getName().compareTo(second.getName());
+
+int compared = comparator.compare(mockito, java);
+
+assertThat(compared, greaterThan(0));
+}
+
+@Test
+public void shouldCompareAndReverseTwoGuidesByUsingComparator() throws Exception {
+CraftCoderGuide mockito = new CraftCoderGuide("Mockito");
+CraftCoderGuide java = new CraftCoderGuide("Java 8");
+
+Comparator<CraftCoderGuide> comparator = (first, second) -> first.getName().compareTo(second.getName());
+
+int compared = comparator.reversed().compare(mockito, java);
+
+assertThat(compared, lessThan(0));
+}
+
+}
+
+class CraftCoderGuide {
+
+private String name;
+
+public CraftCoderGuide(String name) {
+this.name = name;
+}
+
+public String getName() {
+return name;
+}
+
+}