Do you really need OAuth on screen? Have you tried using the consumer key and consumer secret.

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.IOException;
import java.io.UnsupportedEncodingException;

import org.apache.http.Header;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicHeader;
import org.apache.http.util.EntityUtils;

import org.json.JSONException;
import org.json.JSONObject;

/**
 * This program demonstrates the following basic use cases for the REST API:
 * - authentication with OAuth 2.0 (This is for development purposes only. Not a real implementation.)
 * - querying (using account records)
 * - inserting (using a contact record related to one of the retrieved account records)
 * - updating (updates contact record added in previous step)
 * 
 * @author salesforce training
 */
public class REST_Code extends Object {
	//---------Credentials----------
	//Credentials providing access to a specific Salesforce organization.
	private static final String userName = "demo@demo.com"; // COPY USERNAME
	private static final String password = "passwordTOKEN"; // COPY PASSWORD AND TOKEN
	
	//---------REST and OAuth-------
	//Portions of the URI for REST access that are re-used throughout the code
	private static String OAUTH_ENDPOINT = "/services/oauth2/token";
	private static String REST_ENDPOINT = "/services/data";
	
	//Holds URI returned from OAuth call, which is then used throughout the code.
	String baseUri;
	
	//The oauthHeader set in the oauth2Login method, and then added to
	//each HTTP object that is used to invoke the REST API.
	Header oauthHeader;
	
	//Basic header information added to each HTTP object that is used
	//to invoke the REST API.
	Header prettyPrintHeader = new BasicHeader("X-PrettyPrint", "1");

	//----------Data specific---------
	//Retrieved accountId that is used when contact is added.
	private static String accountId;
	
	//Id of inserted contact. Used to update contact.
	private static String contactId;

	//----------Utility-------------
	//Used to get input from console.
	private static BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

	//================Code starts here===================
	public static void main(String[] args) {
		new REST_Code();
	}
	
	/**
	 * This class holds all the values related to the credentials needed to
	 * make the OAuth2 request for authentication. Normally they would not be set in
	 * this manner.
	 */	
	class UserCredentials {
		String loginInstanceDomain = "cs10.salesforce.com"; // COPY YOUR SERVER INSTANCE
		String apiVersion = "27"; // COPY YOU API VERSION
		String userName = REST_Code.userName;
		String password = REST_Code.password;
		String consumerKey = "CONSUMER_KEY"; // COPY YOUR CONSUMER KEY		
		String consumerSecret = "CONSUMER_SECRET"; // COPY YOUR CONSUMER SECRET
		String grantType = "password";
	}

	/**
	 * Constructor drives console interaction and calls appropriate methods.
	 */
	public REST_Code() {

		showMenu();
		boolean invalidValue = true;
		int executionOption = 99;
		String choice = getUserInput("Enter option: ");
		while (invalidValue) {
			try {
				executionOption = Integer.parseInt(choice);
				if ((executionOption < 1 || executionOption > 4) && executionOption!=99) {
					System.out.println("Please enter 1, 2, 3, 4, or 99.\n");
					choice = getUserInput("Enter the number of the sample to run: ");
					showMenu();
				} else {
					invalidValue = false;
				}
			} catch (Exception e) {
				System.out.println("Invalid value. Please enter 1, 2, 3, 4, or 99.\n");
				choice = getUserInput("Enter the number of the sample to run: ");
				showMenu();
			}			
		}
		if (executionOption == 99) {
			System.out.println("No action taken");
		} else {
			//Login is done for option 1, as well as all other valid options.
			this.oauth2Login();
			if (executionOption >= 2) {
				this.restGetExample();
			}
			if (executionOption >= 3) {
				if (accountId != null) {
					this.restPostExample(accountId);           		
				} else {
					System.out.println("Account not found.");
				}
			}
			if (executionOption == 4) {
				if (contactId != null) {
					this.restPatchExample(contactId);
				}  else {
					System.out.println("Contact not found.");
				}
			}	
		}	
		System.out.println("Program complete.");
	}

	/**
	 * This method connects the program to the Salesforce organization using OAuth. 
	 * It stores returned values for further access to organization.
	 * @param userCredentials Contains all credentials necessary for login
	 * @return
	 */
	public HttpResponse oauth2Login() {
		System.out.println("_______________ Login _______________");
		OAuth2Response oauth2Response = null;
		HttpResponse response = null;
		UserCredentials userCredentials = new UserCredentials();
		String loginHostUri = "https://" + userCredentials.loginInstanceDomain + OAUTH_ENDPOINT;
		
		try {
			//Construct the objects for making the request
			HttpClient httpClient = new DefaultHttpClient();
			HttpPost httpPost = new HttpPost(loginHostUri);
			StringBuffer requestBodyText = new StringBuffer("grant_type=password");
			requestBodyText.append("&username=");
			requestBodyText.append(userCredentials.userName);
			requestBodyText.append("&password=");
			requestBodyText.append(userCredentials.password);
			requestBodyText.append("&client_id=");
			requestBodyText.append(userCredentials.consumerKey);
			requestBodyText.append("&client_secret=");
			requestBodyText.append(userCredentials.consumerSecret);
			System.out.println("Enviado: "+requestBodyText.toString());
			StringEntity requestBody = new StringEntity(requestBodyText.toString());
			requestBody.setContentType("application/x-www-form-urlencoded");
			httpPost.setEntity(requestBody);
			httpPost.addHeader(prettyPrintHeader);
			
			//Make the request and store the result
			response = httpClient.execute(httpPost);
			
			//Parse the result if we were able to connect. 
			if (  response.getStatusLine().getStatusCode() == 200 ) {
				String response_string = EntityUtils.toString(response.getEntity());
				try {
					JSONObject json = new JSONObject(response_string);
					oauth2Response = new OAuth2Response(json);
					System.out.println("JSON returned by response: +\n" + json.toString(1));
				} catch (JSONException je) {
					je.printStackTrace();
				}  
				baseUri = oauth2Response.instance_url + REST_ENDPOINT + "/v" + userCredentials.apiVersion +".0";
				oauthHeader = new BasicHeader("Authorization", "OAuth " + oauth2Response.access_token);
				System.out.println("\nSuccessfully logged in to instance: " + baseUri);
			} else {
				System.out.println("An error has occured. Http status: " + response.getStatusLine().getStatusCode());
				System.out.println(getBody(response.getEntity().getContent()));
				System.exit(-1);
			}
		} catch (UnsupportedEncodingException uee) {
			uee.printStackTrace();
		} catch (IOException ioe) {
			ioe.printStackTrace();
		} catch (NullPointerException npe) {
			npe.printStackTrace();
		}
		return response;
	}

	/**
	 * This method demonstrates 
	 * - How to use HTTPGet and a constructed URI to retrieve data from Salesforce.
	 * - Simple parsing of a JSON object. 
	 */
	public void restGetExample() {
		System.out.println("\n_______________ Account QUERY _______________");
		try {
			//Set up the HTTP objects needed to make the request.
			HttpClient httpClient = new DefaultHttpClient();
			String uri = baseUri + "/query?q=SELECT+id+,+name+FROM+Account+limit+1";
			System.out.println("Query URL: " + uri);
			HttpGet httpGet = new HttpGet(uri);
			httpGet.addHeader(oauthHeader);
			httpGet.addHeader(prettyPrintHeader);
			
			// Make the request.
			HttpResponse response = httpClient.execute(httpGet);
			
			// Process the result
			int statusCode = response.getStatusLine().getStatusCode();
			if (statusCode == 200) {
				String response_string = EntityUtils.toString(response.getEntity());
				try {
					JSONObject json = new JSONObject(response_string);
					System.out.println("JSON result of Query:\n" + json.toString(1));					
					accountId = json.getJSONArray("records").getJSONObject(0).getString("Id");
					System.out.println("accountId value is " + accountId);
				} catch (JSONException je) {
					je.printStackTrace();
				}        	  
			} else {
				System.out.println("Query was unsuccessful. Status code returned is " + statusCode);
			}
		} catch (IOException ioe) {
			ioe.printStackTrace();
		} catch (NullPointerException npe) {
			npe.printStackTrace();
		}
	}

	/**
	 * This method demonstrates 
	 * - How to use HTTPPost and a constructed URI to insert data into Salesforce.
	 * - Simple creation of a JSON object. 
	 */
	public void restPostExample(String accountId) {
		System.out.println("\n_______________ Contact INSERT _______________");		
		String uri = baseUri + "/sobjects/Contact/";
		try {
			//create the JSON object containing the new contact details.
			JSONObject contact = new JSONObject();
			contact.put("LastName", "Chin");
			contact.put("FirstName", "Jasmine");
			contact.put("MobilePhone", "(415)222-3333");
			contact.put("Phone", "(650)123-3211");			
			contact.put("AccountId", accountId);
			System.out.println("JSON for contact record to be inserted:\n" + contact.toString(1));

			//Construct the objects needed for the request
			DefaultHttpClient httpClient = new DefaultHttpClient();
			HttpPost httpPost = new HttpPost(uri);
			httpPost.addHeader(oauthHeader);
			httpPost.addHeader(prettyPrintHeader);
			// The message we are going to post
			StringEntity body = new StringEntity(contact.toString(1));
			body.setContentType("application/json");
			httpPost.setEntity(body);

			//Make the request
			HttpResponse response = httpClient.execute(httpPost);

			//Process the results
			int statusCode = response.getStatusLine().getStatusCode();
			if (statusCode == 201) {
				String response_string = EntityUtils.toString(response.getEntity());
				JSONObject json = new JSONObject(response_string);
				// Store the retrieved contact id to use when we update the contact.
				contactId = json.getString("id");
				System.out.println("New contact id from response: " + contactId);     	  
			} else {
				System.out.println("Insertion unsuccessful. Status code returned is " + statusCode);
			}
		} catch (JSONException e) {
			System.out.println("Issue creating JSON or processing results");
			e.printStackTrace();
		} catch (IOException ioe) {
			ioe.printStackTrace();
		} catch (NullPointerException npe) {
			npe.printStackTrace();
		}
	}

	/**
	 * This method demonstrates 
	 * - How to use HTTPPatch and a constructed URI to update data in Salesforce.
	 * NOTE: You have to create the HTTPPatch, as it does not exist in the standard library.
	 * - Simple creation of a JSON object. 
	 */	
	public void restPatchExample(String contactid) {
		System.out.println("\n_______________ Contact UPDATE _______________");
		
		//Notice, the id for the record to update is part of the URI, not part of the JSON
		String uri = baseUri + "/sobjects/Contact/" + contactid;
		try {
			//Create the JSON object containing the updated contact phone number
			//and the id of the contact we are updating.
			JSONObject contact = new JSONObject();
			contact.put("Phone", "(415)555-1234");
			System.out.println("JSON for update of contact record:\n" + contact.toString(1));

			//Set up the objects necessary to make the request.
			DefaultHttpClient httpClient = new DefaultHttpClient();
			HttpPatch httpPatch = new HttpPatch(uri);
			httpPatch.addHeader(oauthHeader);
			httpPatch.addHeader(prettyPrintHeader);
			StringEntity body = new StringEntity(contact.toString(1));
			body.setContentType("application/json");
			httpPatch.setEntity(body);

			//Make the request
			HttpResponse response = httpClient.execute(httpPatch);

			//Process the response
			int statusCode = response.getStatusLine().getStatusCode();
			if (statusCode == 204) {
				System.out.println("Updated the contact successfully.");     	  
			} else {
				System.out.println("Contact update NOT successfully. Status code is " + statusCode);
			}
		} catch (JSONException e) {
			System.out.println("Issue creating JSON or processing results");
			e.printStackTrace();
		} catch (IOException ioe) {
			ioe.printStackTrace();
		} catch (NullPointerException npe) {
			npe.printStackTrace();
		}
	}

	/**
	 * Extend the Apache HttpPost method to implement an HttpPost
	 * method.
	 */
	private static class HttpPatch extends HttpPost {
		public HttpPatch(String uri) {
			super(uri);
		}
		
		public String getMethod() {
			return "PATCH";
		}
	}

	/**
	 * This class is used to hold values returned by the OAuth request.
	 */
	static class OAuth2Response {
		String id;
		String issued_at;
		String instance_url;
		String signature;
		String access_token;

		public OAuth2Response() {
		}
		public OAuth2Response(JSONObject json) {
			try {
				id =json.getString("id");
				issued_at = json.getString("issued_at");
				instance_url = json.getString("instance_url");
				signature = json.getString("signature");
				access_token = json.getString("access_token");

			} catch (JSONException e) {
				e.printStackTrace();
			}
		}
	}

	//==========utility methods=============
	/**
	 * Utility method for changing a stream into a String.
	 * @param inputStream
	 * @return
	 */
	private String getBody(InputStream inputStream) {
		String result = "";
		try {
			BufferedReader in = new BufferedReader(
					new InputStreamReader(inputStream)
			);
			String inputLine;
			while ( (inputLine = in.readLine() ) != null ) {
				result += inputLine;
				result += "\n";
			}
			in.close();
		} catch (IOException ioe) {
			ioe.printStackTrace();
		}
		return result;
	}

	//--------------utility methods for user input----------
	/**
	 * A utility method to be used for getting user input from the console.
	 */
	private String getUserInput(String prompt) {
		String result = "";
		try {
			System.out.print(prompt);
			result = reader.readLine();
		} catch (IOException ioe) {
			ioe.printStackTrace();
		}
		return result;
	}

	/**
	 * Outputs menu choices on console.
	 */
	private void showMenu() {
		System.out.println("");
		System.out.println("");
		System.out.println(" 1. Login Only");
		System.out.println(" 2. Find Account");
		System.out.println(" 3. Insert Contact for Account");
		System.out.println(" 4. Update Contact");
		System.out.println("99. Exit");
		System.out.println("   ");
	}
}