发布时间 : 星期三 文章Java2实用教程(第5版)最新答案-耿祥义更新完毕开始阅读0e48a01ff56527d3240c844769eae009591ba25e
Scanner scanner = new Scanner(cost); scanner.useDelimiter(\ double sum=0; int count =0;
while(scanner.hasNext()){
try{ double score = scanner.nextDouble(); count++; sum = sum+score; System.out.println(score); }
catch(InputMismatchException exp){ String t = scanner.next(); } }
System.out.println(\总分:\分\ System.out.println(\平均分:\分\ } }
习题九(第9章)
一、问答题
1.Frame容器的默认布局是BorderLayout布局。 2.不可以。
3.ActionEvent。 4.DocumentEvent。 5.5个。
6.MouseMotionListener。 二、选择题
1.C。2.A。3.A。4.D。5.C。 三、编程题
1. import java.awt.*;
import javax.swing.event.*; import javax.swing.*; import java.awt.event.*; public class E {
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(\ sum=0; aver=0;
for(int i=0;i 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(); } }