Insert or NonExecutable Query of MySql in java

For queries like insert or delete or Update use these codes in java for MySql::

public boolean insert_ip_loggedin(String ip,int user_id)
{
try {
Statement s3 = conn.createStatement();

s3.execute("insert into logged_in(user_id,logged_ip,logged_now) values('"+user_id+"','"+ip+"','yes')");
s3.close ();
return true;
}
catch(Exception e){
String err = "Cannot connect to database server: "+e.getMessage();
JOptionPane.showMessageDialog(null,"Please click logout before exiting", "Information", JOptionPane.INFORMATION_MESSAGE);
return false;
}

}