title: How to concatenate variable arguments of string
body: <p>I need to concatenate a variable number of arguments (type String) to one String:</p>
  
  <p>E.g.:</p>
  
  <pre><code>System.out.println( add("ja", "va") );
  </code></pre>
  
  <p>should return <code>java</code> but my implementation returns <code>jaja</code>.  </p>
  
  <p>I tried this:</p>
  
  <pre><code>public static String add(String... strings) {
      for (String arg : strings) {
          return String.format(arg.concat(arg));
      }
      return "string";
  }
  </code></pre>
  
  <p>What am I doing wrong?</p>