This code sample demonstrates, how to connect to salesforce using partner jar generated from partner WSDL using WSC jar provided by salesforce.

PartnerExample.java

package partner;

import com.sforce.soap.partner.Connector;
import com.sforce.soap.partner.DeleteResult;
import com.sforce.soap.partner.PartnerConnection;
import com.sforce.soap.partner.QueryResult;
import com.sforce.soap.partner.SaveResult;
import com.sforce.soap.partner.Error;
import com.sforce.soap.partner.sobject.SObject;
import com.sforce.ws.ConnectionException;
import com.sforce.ws.ConnectorConfig;

public class PartnerExample {
  
  //Hardcoded username and password  
  static final String USERNAME = "USERNAME here";
  static final String PASSWORD = "Password + Security token here";
  static PartnerConnection connection;

  public static void main(String[] args) {

    //Creating connector config instance with username and password
    ConnectorConfig config = new ConnectorConfig();
    config.setUsername(USERNAME);
    config.setPassword(PASSWORD);
    
    try {
    	
      //Passing configuration to connection object    
      connection = Connector.newConnection(config);
      
      //If connection is successful session Id can be obtained with below line
      System.out.println("SessionId: "+config.getSessionId());
                  
      //Once connection is established records can be queried as below
      QueryResult queryResults = connection.query("SELECT Id, FirstName, LastName FROM Contact LIMIT 5");    
      
      //Query results can be be convereted to sobject array using below method
      SObject[] sObjList = queryResults.getRecords();
      for(SObject so:sObjList){
    	  System.out.println("Query Result"+so);
      }
        
      //New records are created in salesforce using below lines,
      SObject[] records = new SObject[1];
      SObject so = new SObject();
      so.setType("Account");
      so.setField("Name", "SOAP Testing Account");
      records[0] = so;
      SaveResult[] saveResults = connection.create(records);
      System.out.println("Account Creation"+saveResults);
      for(SaveResult sr:saveResults){
    	  System.out.println("Account Creation"+sr);
      }
        
    } catch (ConnectionException e1) {
        e1.printStackTrace();
    }  

  }
}