Stand 001/14.10/15:56

src/ErrorWriter.java

@@ -0,0 +1,6 @@
+public class ErrorWriter implements HelloWorldWriter {
+
+    public void writeHelloWorld() {
+        System.err.println("Hello");
+    }
+}

src/Executor.java

@@ -0,0 +1,15 @@
+public class Executor {
+    public static void main(String[] args){
+        printHelloWorld(new ErrorWriter(), new ErrorWriter(), true);
+    }
+    public static void printHelloWorld(HelloWorldWriter writer1,
+                                       HelloWorldWriter writer2, boolean second){
+
+        if(second){
+            writer2.writeHelloWorld();
+
+        } else{
+            writer1.writeHelloWorld();
+        }
+    }
+}

src/HelloWorld.java

@@ -1,6 +0,0 @@
-public class HelloWorld {
-    public static void main(String[] args) {
-
-        System.out.println("Hello World!");
-    }
-}

src/HelloWorldWriter.java

@@ -0,0 +1,6 @@
+
+public interface HelloWorldWriter
+{
+    void writeHelloWorld();
+
+}

src/OutWriter.java

@@ -0,0 +1,8 @@
+
+public class OutWriter implements HelloWorldWriter{
+
+    public void writeHelloWorld() {
+        System.out.println("Hello");
+    }
+
+}