How to count the parameters that will be passed through POST JAVA?

Question

Java

Here is a sample code:
public HttpRequest(InputStream input) {
this.request = convertInputStreamToString(input);
this.uri = parseUri(request);
this.parameterMap = parseParameterMap(request);
}
The method parseParameterMap (private Map parseParameterMap(String request)) should parse the parameters that are passed via POST. What needs to be parsed to count them. Thanks