《java2实用教程》(第四版)课后答案 第九章-第十三章.doc

Java作业4（第九章---第十三章） 第九章 3.1.1程序代码 import java.awt.*; import javax.swing.event.*; import javax.swing.*; import java.awt.event.*; public class kehou31 { public static void main(String args[]) { Computer fr=new Computer(); } } class Computer extends JFrame implements DocumentListener { JTextArea text1,text2; int count=1; double sum=0,aver=0; Computer() { setLayout(new FlowLayout()); text1=new JTextArea(6,20); text2=new JTextArea(6,20); add(new JScrollPane(text1)); add(new JScrollPane(text2)); text2.setEditable(false); (text1.getDocument()).addDocumentListener(this); setSize(300,320); setVisible(true); validate(); setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); } public void changedUpdate(DocumentEvent e) { String s=text1.getText(); String []a =s.split([^0123456789.]+); sum=0; aver=0; for(int i=0;ia.length;i++) { try { sum=sum+Double.parseDouble(a[i]); } catch(Exception ee) {} } count=a.length; aver=sum/count; text2.setText(null); text2.append(\n和:+sum); text2.append(\n平均值:+aver); } public void removeUpdate(DocumentEvent e){ changedUpdate(e); } public void insertUpdate(DocumentEvent e){ changedUpdate(e); } } 3.1.2 运行界面 3.2.1程序代码 import java.awt.*; import javax.swing.event.*; import javax.swing.*; import java.awt.event.*; public class kehou932 { public static void main(String args[]) { ComputerFrame fr=new ComputerFrame(); fr.setBounds(100,100,650,120); fr.setTitle(多功能计算器); fr.setBackground(Color.blue); } } 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);