request.getParameterMap()

  
The getParameterMap() returns a Map that has Strings as keys and String[] as values. That's so you can have ?x=1&x=2&x=3 in your URL query string. The keys in the Map must be unique but there can be multiple values for each key.

So.. when you pull a value out of a Map created by the getParameterMap() method you must cast it to a String[] or else you'll get the value's location in memory instead of it's actual value. If you're writing the code and know for a fact that you'll always have only one value for each param then you can just use yourVar[0] but if there may be multiple values for each key then you'll need to loop over each value array.


Code :

Map params = request.getParameterMap();

Iterator i = params.keySet().iterator();

while ( i.hasNext() )

  {

    String key = (String) i.next();

    String value = ((String[]) params.get( key ))[ 0 ];

  }

Code :

Map param_map = request.getParameterMap();

if (param_map == null)

    throw new ServletException(

      "getParameterMap returned null in: " + getClass().getName());

 //iterate through the java.util.Map and display posted parameter values

//the keys of the Map.Entry objects ae type String; the values are type String[],

//or String array

Iterator iterator = param_map.entrySet().iterator();

while(iterator.hasNext()){

    Map.Entry me = (Map.Entry)iterator.next();

    out.println(me.getKey() + ": ");

    String[] arr = (String[]) me.getValue();

    for(int i=0;i<arr.length;i++){

      out.println(arr[i]);

      //print commas after multiple values, 

      //except for the last one

      if (i > 0 && i != arr.length-1)

        out.println(", ");}//end for

        out.println("<br><br>");

    }//end while

refer: http://snippets.dzone.com/posts/show/3491     http://www.java2s.com/Code/Java/Servlets/PostHandler.htm