if you don't know that, you shouldn't bother to work with Swing GUI's and start learning the basics of OO design and Java.
for some reason, you've asked about this "all over the forum"
but, just to indulge you one last time:
String sql = "Select * from tbkaryawan where IDKaryawan='"+jTextField1.getText()+"'&&Password='"+ new String(jPasswordField1.getPassword()) + "'";
now, in the hope to give you a reality check: you seem to have trouble replacing one method by the other. you seem to have difficulties instantiating a String object. when provided with the code you need, you don't know how to copy paste it (which is basically all you needed to do).
stop working on GUI's, stop working with databases, and first make sure you have a sound knowledge of the basics. if you don't, you'll have this kind of problems every single time you're trying something you haven't done yet, and that isn't solved in the very exact same way.