add examples in java 8 (#12)

* code for chapters 3-9 in Java

* code for chapters 1 in Java

* code for chapter 2 in Java

* missing CheckVoter for chapter 5 in Java

* add missing sample output for SetCovering as a comment

03_recursion/java/02_greet/src/Greet.java

@@ -0,0 +1,21 @@
+public class Greet {
+
+    private static void greet2(String name) {
+        System.out.println("how are you, " + name + "?");
+    }
+
+    private static void bye() {
+        System.out.println("ok bye!");
+    }
+
+    private static void greet(String name) {
+        System.out.println("hello, " + name + "!");
+        greet2(name);
+        System.out.println("getting ready to say bye...");
+        bye();
+    }
+
+    public static void main(String[] args) {
+        greet("adit");
+    }
+}