title: How to declare HashMap in global and add values into it only for the first time?
body: <p>I am using an HashMap in every method and adding values to it, like this...</p>
  
  <pre><code>LinkedHashMap&lt;String,String&gt; ProductList = new LinkedHashMap&lt;String,String&gt;();
      ProductList.put("107070706", "Hello");
      ProductList.put("107070707", "Bye");
      ProductList.put("107070708", "World");
      ProductList.put("107070709", "SeeYou");
  </code></pre>
  
  <p>I want to declare it inside the class and has to assign values so that I can use this later in my own methods...</p>
  
  <p>How can I do that?</p>
  
  <p>Note: I got an idea to implement this adding elements part in a constructor, but It doesn't fit to my requirement.</p>