Added examples.

examples/java/src/main/java/App.java

@@ -0,0 +1,12 @@
+/*
+ * This Java source file was generated by the Gradle 'init' task.
+ */
+public class App {
+    public static void main(String[] args) {
+        System.out.println(new App().getGreeting());
+    }
+
+    public String getGreeting() {
+        return "Hello world.";
+    }
+}

examples/java/src/test/java/AppTest.java

@@ -0,0 +1,11 @@
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+class AppTest {
+    @Test
+    void testAppHasAGreeting() {
+        App classUnderTest = new App();
+        assertNotNull("app should have a greeting", classUnderTest.getGreeting());
+    }
+}