Add interpreter design pattern with test case (#59)

Author: mperor

DesignPatterns/README.md

@@ -12,6 +12,7 @@ with practical examples and best practices for using design patterns to create r
 - [Chain of Responsibility](src/main/java/pl/mperor/lab/java/design/pattern/behavioral/chain/of/responsibility) 🔗
 - [Command](src/main/java/pl/mperor/lab/java/design/pattern/behavioral/command) 📝
 - [Execute Around Method (EAM)](src/main/java/pl/mperor/lab/java/design/pattern/behavioral/eam) ⭕
+- [Interpreter](src/main/java/pl/mperor/lab/java/design/pattern/behavioral/interpreter) 📰
 - [Mediator](src/main/java/pl/mperor/lab/java/design/pattern/behavioral/mediator) 🗣️
 - [Memento](src/main/java/pl/mperor/lab/java/design/pattern/behavioral/memento) 💾
 - [Observer](src/main/java/pl/mperor/lab/java/design/pattern/behavioral/observer) 👀

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/interpreter/CommandInterpreter.java

@@ -0,0 +1,7 @@
+package pl.mperor.lab.java.design.pattern.behavioral.interpreter;
+
+@FunctionalInterface
+interface CommandInterpreter {
+
+    String interpret(String source);
+}

DesignPatterns/src/test/java/pl/mperor/lab/java/design/pattern/behavioral/interpreter/CommandInterpreterTest.java

@@ -0,0 +1,24 @@
+package pl.mperor.lab.java.design.pattern.behavioral.interpreter;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class CommandInterpreterTest {
+
+    @Test
+    public void testCommandInterpreter() {
+        Map<String, CommandInterpreter> commands = new HashMap<>();
+        commands.put("/welcome", name -> "👋 Welcome " + name + "!");
+        commands.put("/shout", message -> "❗" + message.toUpperCase());
+
+        Assertions.assertEquals("👋 Welcome Alice 👱‍♀️!",
+                commands.get("/welcome").interpret("Alice 👱‍♀️")
+        );
+        Assertions.assertEquals("❗ARE U READY?",
+                commands.get("/shout").interpret("Are u ready?")
+        );
+    }
+}