This is code snippet to get the calendar events of a user in java code (tested)

pom.xml

<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpclient -->
<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.2</version>
</dependency>

<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpcore -->
<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpcore</artifactId>
    <version>4.4.5</version>
</dependency>

<!-- https://mvnrepository.com/artifact/commons-logging/commons-logging -->
<dependency>
    <groupId>commons-logging</groupId>
    <artifactId>commons-logging</artifactId>
    <version>1.2</version>
</dependency>

SakaiUtil.java

package com;



import com.fasterxml.jackson.databind.ObjectMapper;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.CookieStore;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.protocol.HttpClientContext;
import org.apache.http.impl.client.BasicCookieStore;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.protocol.BasicHttpContext;
import org.apache.http.protocol.HttpContext;
import org.apache.http.util.EntityUtils;

/**
 * Created by Chaitanya on 11/14/2016.
 */

public class SakaiUtil{

	public static void main(String ar[]) throws ClientProtocolException, IOException{
		String url = "https://qa10-mysql.nightly.sakaiproject.org";
        String username = "admin";
        String password = "admin";
        getEventsResponse(url, username, password);
	}
	
    public static final String TAG = "SakaiUtil";
    ObjectMapper mapper = new ObjectMapper();
    public static String getEventsResponse(final String url, final String username, final String password) {
        try {
            System.out.println("getEventsResponse");
            List<NameValuePair> params = new ArrayList<>();

            params.add(new BasicNameValuePair("_username", username));
            params.add(new BasicNameValuePair("_password", password));

            //create httpclient
            HttpClient httpClient = HttpClientBuilder.create().build();
           
            //store cookies in context
            CookieStore cookieStore = new BasicCookieStore();
            HttpContext httpContext = new BasicHttpContext();
            httpContext.setAttribute(HttpClientContext.COOKIE_STORE, cookieStore);
            
            //call login web service
            String webserviceURL = url+"/direct/session/new";
            HttpPost postRequest = new HttpPost(webserviceURL);
            postRequest.setHeader("Content-Type", "application/x-www-form-urlencoded");
            postRequest.setEntity(new UrlEncodedFormEntity(params));
            HttpResponse response = httpClient.execute(postRequest, httpContext);
            
            //get the status code
            int status = response.getStatusLine().getStatusCode();
            
            //if status code is 201 login is successful. So reuse the httpContext for next requests.
            //if status code is not 201, there is a problem with the request.
            if(status!=201)
                return null;
            EntityUtils.consume( response.getEntity() );
            System.out.println("status:"+status);
            String responseVal = getCalendarData(httpContext, url);
            System.out.println("responseVal:"+responseVal);
            //Log.i(TAG, "responseVal:"+responseVal);
            //CalendarResponse calendarResponse = formatJSON(responseVal);
            return responseVal;
        }catch(IOException e){
            e.printStackTrace();
            return null;
        }
    }

    protected static String getCalendarData(HttpContext httpContext, final String url) throws IOException {
       
        HttpClient httpClient = HttpClientBuilder.create().build();
        String webserviceURL = url+"/direct/calendar/my.json";
        HttpGet getRequest = new HttpGet(webserviceURL);

        HttpResponse response = httpClient.execute(getRequest, httpContext);

        HttpEntity httpEntity = response.getEntity();
        String responseVal = EntityUtils.toString(httpEntity);
        //Log.i(TAG, "responseVal:"+responseVal);
        EntityUtils.consume(httpEntity);
        return  responseVal;
    }

}