How to read the parameters and value from the query-string using java?

Ok in my case I had the querystring from another source so you maybe need this:

    public static Map<String, String> getQueryMap(String query)  
{  
    String[] params = query.split("&");  
    Map<String, String> map = new HashMap<String, String>();  
    for (String param : params)  
    {  String [] p=param.split("=");
        String name = p[0];  
      if(p.length>1)  {String value = p[1];  
        map.put(name, value);
      }  
    }  
    return map;  
} 

So then you can use:

 Map params=getQueryMap(querystring);
 String id=(String)params.get("id");
 String anotherparam=(String)params.get("anotherparam");

A solution with Java 8.

This piece of code transform the query string in a key/value list:

List<AbstractMap.SimpleEntry<String, String>> list = 
        asList(queryString.split("&")).stream()
        .map(s -> copyOf(s.split("="), 2))
        .map(o -> new AbstractMap.SimpleEntry<String, String>(o[0], o[1]) )
        .collect(toList());

the comment of @Tuno inspired me to write a new answer, this alternative (and shorter) solution use groupingBy method:

Map<String, List<String>> llist = 
       asList(queryString.split("&")).stream()
       .map(s -> copyOf(s.split("="), 2))
       .collect(groupingBy(s -> s[0], mapping(s -> s[1], toList())));

I suggest to decode the values with URLDecoder.decode(String s, String enc)

Both the solutions prints collection content with this line:

list.stream().forEach(s -> System.out.println(s.getKey() + " = " + s.getValue()));

public void doGet(HttpServletRequest request, HttpServletResponse response) {
    String searchString = request.getParameter("searchString");
    // process searchString
}

Decoding the parameter is done automatically.