Added 25 solutions

Java/Advanced/Java Singleton Pattern/Solution.java

@@ -0,0 +1,18 @@
+//     Author: Rodney Shaghoulian
+//     Github: github.com/rshaghoulian
+// HackerRank: hackerrank.com/rshaghoulian
+
+import java.util.Scanner;
+import java.lang.reflect.Constructor;
+
+class Singleton {
+    private Singleton() {}
+    public String str;
+    private static Singleton instance = null;
+    public static Singleton getSingleInstance() {
+        if (instance == null) {
+            instance = new Singleton();
+        }
+        return instance;
+    }
+}