java2实用教程第5版第九章,Java2实用教程（第5版）最新答案-耿祥义

try { sum=sum+Double.parseDouble(a[i]); }

catch(Exception ee) {} }

aver=sum/count; text2.setText(null); text2.append(\和:\ text2.append(\平均值:\ }

public void removeUpdate(DocumentEvent e){ changedUpdate(e); }

public void insertUpdate(DocumentEvent e){ changedUpdate(e); } }

2. import java.awt.*;

import javax.swing.event.*; import javax.swing.*; import java.awt.event.*; public class E {

public static void main(String args[]) {

ComputerFrame fr=new ComputerFrame(); } }

class ComputerFrame extends JFrame implements ActionListener { JTextField text1,text2,text3;

JButton buttonAdd,buttonSub,buttonMul,buttonDiv; JLabel label;

public ComputerFrame() { setLayout(new FlowLayout()); text1=new JTextField(10); text2=new JTextField(10); text3=new JTextField(10);

label=new JLabel(\ label.setBackground(Color.green); add(text1); add(label); add(text2); add(text3);

buttonAdd=new JButton(\加\ buttonSub=new JButton(\减\ buttonMul=new JButton(\乘\ buttonDiv=new JButton(\除\ add(buttonAdd); add(buttonSub); add(buttonMul); add(buttonDiv);

buttonAdd.addActionListener(this); buttonSub.addActionListener(this); buttonMul.addActionListener(this); buttonDiv.addActionListener(this); setSize(300,320); setVisible(true); validate();

setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); }

public void actionPerformed(ActionEvent e) { double n;

if(e.getSource()==buttonAdd) { double n1,n2;

try{ n1=Double.parseDouble(text1.getText()); n2=Double.parseDouble(text2.getText()); n=n1+n2;

text3.setText(String.valueOf(n)); label.setText(\

}

catch(NumberFormatException ee) { text3.setText(\请输入数字字符\ } }

else if(e.getSource()==buttonSub) { double n1,n2;

try{ n1=Double.parseDouble(text1.getText()); n2=Double.parseDouble(text2.getText()); n=n1-n2;

text3.setText(String.valueOf(n)); label.setText(\ }

catch(NumberFormatException ee) { text3.setText(\请输入数字字符\ } }

else if(e.getSource()==buttonMul) {double n1,n2;

try{ n1=Double.parseDouble(text1.getText()); n2=Double.parseDouble(text2.getText()); n=n1*n2;

text3.setText(String.valueOf(n)); label.setText(\ }

catch(NumberFormatException ee) { text3.setText(\请输入数字字符\ } }

else if(e.getSource()==buttonDiv) {double n1,n2;

try{ n1=Double.parseDouble(text1.getText()); n2=Double.parseDouble(text2.getText()); n=n1/n2;

text3.setText(String.valueOf(n)); label.setText(\ }

catch(NumberFormatException ee) { text3.setText(\请输入数字字符\ } } validate(); } }