import javax.net.ssl.HttpsURLConnection;
import java.io.*;
import java.net.URL;
import java.util.Base64;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class OauthAuthentication {
	private static final Pattern pat = Pattern.compile(".*\"access_token\"\\s*:\\s*\"([^\"]+)\".*");
	private static final String clientId = "jdiwiweoiwe.NxkdgEZTQHC3SvdVQyFm5eSmbiDCQ";//clientId
	private static final String clientSecret = "fhdkhskjs";//client secret
	private static final String tokenUrl = 'https://login.salesforce.com/services/oauth2/token";
	private static final String auth = clientId + ":" + clientSecret;
	private static final String authentication = Base64.getEncoder().encodeToString(auth.getBytes());
	private static String userName="xyz";
	private static String password="abc";
	public static void main(String[] args) throws IOException 
	{
	
	//Username is netId for the person making the call and the password is there password
	String content = "grant_type=password&username=" + userName + "&password=" + password;
    BufferedReader reader = null;
    HttpsURLConnection connection = null;
    String returnValue = "";
    try {
    	System.out.println("authentication"+authentication);
        URL url = new URL(tokenUrl);
        connection = (HttpsURLConnection) url.openConnection();
        connection.setRequestMethod("POST");
        connection.setDoOutput(true);
        connection.setRequestProperty("Authorization", "Basic " + authentication);
        connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
        connection.setRequestProperty("Accept", "application/json");
       
        PrintStream os = new PrintStream(connection.getOutputStream());
        os.print(content);
        os.close();
        System.out.println("content"+content);
        /*reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
        String line = null;
        StringWriter out = new StringWriter(connection.getContentLength() > 0 ? connection.getContentLength() : 2048);
        while ((line = reader.readLine()) != null) {
            out.append(line);
        }
        String response = out.toString();
        System.out.println("output="+response);
        Matcher matcher = pat.matcher(response);
        if (matcher.matches() && matcher.groupCount() > 0) {
            returnValue = matcher.group(1);
        }*/
        System.out.println("response : " + connection.getResponseMessage());
 
    } catch (Exception e) 
    {
        System.out.println("Error : " + e.getMessage()+"\n"+e.getCause()+"\n"+e.getStackTrace()+"\n"+e.getLocalizedMessage());
    } finally {
        if (reader != null) {
            try {
                reader.close();
            } catch (IOException e) {
            }
        }
        connection.disconnect();
    }
	}
}