title: A map within a map vs split the key of type String, which will perform faster?
body: <p>I have a map as <code>Map&lt;String,String&gt;</code> 
  and the entries are like <code>map.put("c_09.01--x28", "OTH")</code>. In this I use split the key and use the <code>x28</code> to change it to <code>OTH</code>.  So my question is whether I should use split operation or use map within a map and <code>map.put("c_09.01", newMap)</code> where newMap will have <code>map.put("x28", 'OTH')</code>. Which one will give me better performance? sample code where I have used that is </p>
  
  <pre><code>for (Entry&lt;String,String&gt; sheetEntry : this.getSheetCD().getUserDefinedSheetCodeMap().entrySet()) {
      String Key = sheet.getKey().split("--")[1];
      int sheetIndex = template.getSheetIndex(sheetKey);
      if(sheetEntry.getKey().toUpperCase().startsWith(getFileName()){ 
          String newSheetName = sheetEntry.getValue();
          template.setSheetName(sheetIndex, newSheetName);    
          }
  }
  </code></pre>
  
  <p>Please let me know if more information is needed. Regards.</p>