我将您的Layout更改JPanel为GridLayout，因此它的大小仅由Layoutmanager处理，取决于面板上的组件。
JFrame f = new JFrame();
f.setLayout(new BorderLayout());
f.setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);
JPanel p = new JPanel(new GridLayout(0, 5));
JScrollPane jsp = new JScrollPane(p);
jsp.setPreferredSize(new Dimension(300,300));
jsp.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED);
jsp.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED);
for (int i = 0; i < 100; i++) {
JButton b = new JButton("Button " + i);
p.add(b);
}
f.add(jsp, BorderLayout.CENTER);
f.setLocation(300, 300);
f.setVisible(true);
f.pack();
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