java - Why does importing JFrame require inheritance but FlowLayout, JLabel, etc not? -

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i started learning guis , watching tutorial "thenewboston" wrote this. don't understand why jframe import that's inherited? i'm not sure if 1 of cases has because java give error otherwise.

import java.awt.flowlayout; import javax.swing.jframe; import javax.swing.jlabel;  public class tuna extends jframe {      private jlabel item1;      public tuna(){         super("the title bar");         setlayout(new flowlayout());                     item1 = new jlabel("this sentence.");         item1.settooltiptext("this gonna show on hover");         add(item1);     } }

jframe not require inheritance. in fact should not use inheritance.

look @ framedemo.java code swing tutorial on how make frames better design.

also, java class names should start upper case character. stick swing tutorials instead of current tutorials looking at.


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