Added 20 solutions

Java/Strings/Java Regex 3 - Username Checker/Solution.java

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+//     Author: Rodney Shaghoulian
+//     Github: github.com/rshaghoulian
+// HackerRank: hackerrank.com/rshaghoulian
+
+import java.io.*;
+import java.util.*;
+import java.text.*;
+import java.math.*;
+import java.util.regex.*;
+
+public class Solution {
+   public static void main(String[] args){
+      Scanner in = new Scanner(System.in);
+      int testCases = Integer.parseInt(in.nextLine());
+      while(testCases>0){
+         String username = in.nextLine();
+         //String pattern = Complete this line in the editable area below  
+         String pattern = "^[a-zA-Z]\\w{7,29}$";
+
+         Pattern r = Pattern.compile(pattern);
+         Matcher m = r.matcher(username);
+          
+         if (m.find( )) {
+            System.out.println("Valid");
+         } else {
+            System.out.println("Invalid");
+         }
+         testCases--;
+      }
+   }
+}