title: FreeMarker get variable value by concatenating another variable value
body: <pre><code>public class Main {
      public static void main(String[] args) throws IOException, TemplateException{
          Configuration freemarkerConfig = new Configuration();
          freemarkerConfig.setClassForTemplateLoading(Main.class, "");
          Template template = freemarkerConfig.getTemplate("template.ftl");
  
          Map&lt;String, String&gt; data = new HashMap&lt;String, String&gt;();
  
          for(int i=1;i&lt;=10;i++){
             data.put("map_"+i, "value"+i);
          }
          Writer out = new StringWriter();
          template.process(data, out);
          System.out.println(out.toString());
      }
  }
  </code></pre>
  
  <p>Here is my FTL code to access  the variable:</p>
  
  <pre><code>&lt;#assign containerIndex=1&gt;
  ${map_containerIndex} 
  This gives error
  I want to evaluate ${map_1}
  </code></pre>