问java中的字符串匹配操作

EN

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.*;
import javax.swing.JFrame;
public class NewJFramefin extends javax.swing.JFrame implements ActionListener
{  

public NewJFramefin() 
{
    initComponents();
    add(jl1);
    add(jf1);
    jb1.setActionCommand("OK");
    jb1.addActionListener(this);
    add(jb1);
    jb2.setActionCommand("CANCEL");
    jb2.addActionListener(this);
    add(jb2);
    jb3.addActionListener(this);
    add(jb3);
}

public void closewindow() 
{
   System.exit(1);

}
public void actionPerformed(ActionEvent e)
{
      String find=jf1.getText();
      String ev=e.getActionCommand();
      String check;
      String str="jdbc:odbc:dsn1";
      try
      {
          Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
          Connection con=DriverManager.getConnection(str);
          Statement s=con.createStatement();
          s.execute("select * from Table1");
          ResultSet res=s.getResultSet();
          if(res!=null)
          {
              while(res.next())
              {
                  check=res.getString(1);
                  System.out.println("STRING FROM DB:"+check + find);
                  if(check==find)
                  {
                       System.out.println("MEANING:"+res.getString(2));
                  }
                  if(ev.equalsIgnoreCase("OK") &&(find.equalsIgnoreCase(check)))
                  {
                      jf2.setText(res.getString(2));
                      add(jf2);

                  }
                  else if(ev.equalsIgnoreCase("CANCEL"))
                  {
                      jf2.setText(" cancelled    ");
                      add(jf2);
                      jf1.setText("    ");
                      add(jf1);
                  }
                  else if(ev.equalsIgnoreCase("EXIT"))
                  {

                      closewindow();
                  }

               }
          }


      }           
      catch(Exception ew)
      {

      }
}


public static void main(String args[]) 
{
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new NewJFramefin().setVisible(true);
        }
    });
}
}