Add Template Method design pattern

README.md

@@ -19,6 +19,7 @@ cd java-patterns-and-constructs
 * [Factory Method](src/main/java/com/penapereira/example/constructs/factorymethod/)
 * [Observer](src/main/java/com/penapereira/example/constructs/observer/)
 * [Singleton](src/main/java/com/penapereira/example/constructs/singleton/)
+* [Template Method](src/main/java/com/penapereira/example/constructs/templatemethod/)
 ### Constructs and Problems
 * [Producer/Consumer](src/main/java/com/penapereira/example/constructs/producerconsumer/), a multi-process synchronization problem.
 

src/main/java/com/penapereira/example/constructs/templatemethod/AbstractClass.java

@@ -0,0 +1,12 @@
+package com.penapereira.example.constructs.templatemethod;
+
+public abstract class AbstractClass {
+
+    protected abstract String stepOne();
+
+    protected abstract String stepTwo();
+
+    public final String templateMethod() {
+        return stepOne() + " then " + stepTwo();
+    }
+}

src/main/java/com/penapereira/example/constructs/templatemethod/ConcreteClassA.java

@@ -0,0 +1,14 @@
+package com.penapereira.example.constructs.templatemethod;
+
+public class ConcreteClassA extends AbstractClass {
+
+    @Override
+    protected String stepOne() {
+        return "A step one";
+    }
+
+    @Override
+    protected String stepTwo() {
+        return "A step two";
+    }
+}

src/main/java/com/penapereira/example/constructs/templatemethod/ConcreteClassB.java

@@ -0,0 +1,14 @@
+package com.penapereira.example.constructs.templatemethod;
+
+public class ConcreteClassB extends AbstractClass {
+
+    @Override
+    protected String stepOne() {
+        return "B step one";
+    }
+
+    @Override
+    protected String stepTwo() {
+        return "B step two";
+    }
+}

src/main/java/com/penapereira/example/constructs/templatemethod/TemplateMethodExampleRunner.java

@@ -0,0 +1,24 @@
+package com.penapereira.example.constructs.templatemethod;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.stereotype.Component;
+
+import com.penapereira.example.constructs.app.ExampleRunnerInterface;
+
+@Component
+public class TemplateMethodExampleRunner implements ExampleRunnerInterface {
+
+    private static final Logger log = LoggerFactory.getLogger(TemplateMethodExampleRunner.class);
+
+    @Override
+    public void runExample() throws Exception {
+        log.trace("Executing Template Method Pattern Implementation");
+
+        AbstractClass a = new ConcreteClassA();
+        log.trace("  " + a.templateMethod());
+
+        AbstractClass b = new ConcreteClassB();
+        log.trace("  " + b.templateMethod());
+    }
+}

src/test/java/com/penapereira/example/constructs/templatemethod/TemplateMethodExampleRunnerTests.java

@@ -0,0 +1,10 @@
+package com.penapereira.example.constructs.templatemethod;
+
+import org.junit.jupiter.api.Test;
+
+class TemplateMethodExampleRunnerTests {
+    @Test
+    void runExampleRuns() throws Exception {
+        new TemplateMethodExampleRunner().runExample();
+    }
+}

src/test/java/com/penapereira/example/constructs/templatemethod/TemplateMethodTests.java

@@ -0,0 +1,14 @@
+package com.penapereira.example.constructs.templatemethod;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.*;
+
+class TemplateMethodTests {
+    @Test
+    void templateMethodRunsSteps() {
+        AbstractClass a = new ConcreteClassA();
+        assertEquals("A step one then A step two", a.templateMethod());
+        AbstractClass b = new ConcreteClassB();
+        assertEquals("B step one then B step two", b.templateMethod());
+    }
+}