我的代码为什么不显示垂直滚动条是那里错了么如果有错求高手修改importjavax.swing.*;importjava.awt.*;importjava.awt.event.*;importjava.util.*;publicclassCai{privateJFrame_fra...

我的代码为什么不显示垂直滚动条 是那里错了么 如果有错 求高手修改

import javax.swing.*;

import java.awt.*;

import java.awt.event.*;

import java.util.*;

public class Cai {

private JFrame _frame;

private JPanel _panelMain;

private JPanel _panelCai;

private JPanel _panelArea;

private JButton _bntCai;

private JTextArea _txtArea;

private JLabel _lbl;

private JTextField _txt;

private JScrollPane _jsp;

public Cai(){

_frame=new JFrame();

_panelMain=new JPanel(new BorderLayout());

_panelCai=new JPanel();

_lbl=new JLabel("请猜1-10之间的数字：");

_panelArea=new JPanel();

_txt=new JTextField(3);

_txtArea=new JTextArea();

_bntCai=new JButton("猜");

_jsp=new JScrollPane(_txtArea);

_panelArea.add(_txtArea);

_panelCai.add(_lbl);

_panelCai.add(_txt);

_panelCai.add(_bntCai);

_panelMain.add(_panelCai,BorderLayout.NORTH);

_panelMain.add(_txtArea,BorderLayout.CENTER);

//_panelMain.add(_jsp,BorderLayout.EAST);

_jsp.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);

_frame.setContentPane(_panelMain);

_frame.setBounds(300,300,300,300);

_frame.setVisible(true);

}

}

public static void main(String[] args) {

Cai a =new Cai();

}

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