How to set the size of a form in java

//The code is as follows:

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//ButtonTest.java

Import? Java . awt . flow layout；

Import? javax . swing . jbutton；

Import? javax . swing . jframe；

Public? Class? ButtonTest？ Extension? JFrame？ {

Public? ButtonTest()？ {

This.setLayout (new? FlowLayout())；

For what? (int？ Me? =? 1; ? Me? & lt=? 1 1; ? i++)？ {

This.add (new? JButton ("button"? +? I))；

}

this.setBounds(200，？ 100,? 300,? 200);

this . set visible(true)；

this . setdefaultcloseoperation(JFrame。 EXIT _ ON _ CLOSE)；

}

Public? Static electricity Invalid? main(String[]？ args)？ {

ButtonTest？ bt？ =? New? button test()；

}

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The operation interface is as follows: