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/03_factorial/src/Factorial.java

@@ -0,0 +1,14 @@
+public class Factorial {
+
+    private static int fact(int x) {
+        if (x == 1) {
+            return 1;
+        } else {
+            return x * fact(x - 1);
+        }
+    }
+
+    public static void main(String[] args) {
+        System.out.println(fact(5));
+    }
+}