Exercises 2.7 Fill in theblanks in each of the following statements: a) Comments areused to document a program and improve its readability. b) A decision can be madein a Java program with a(n) if statement. c) Calculations are normallype

1. 创建一用户界面窗口有两栏，其中一栏显示"北京","大连","武汉","上海","杭州","南京","广州","昆明"，您可以从中选择您最喜欢的城市，另一栏显示六种品牌的电脑"宏基 "、"NEC"、"联想"、"北大方正"、"DELL"、"Applet"。这两个列表可以实现单选和多选，Shift+鼠标点击项可以进行列表数据项的连续选择，Ctrl+鼠标点击项可以进行列表数据项的不连续选项。

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import java.util.Vector;

public class Eg_1 {

JFrame  f;

public  Eg_1(){

f=new JFrame();

Container  con=f.getContentPane();

con.setLayout(new GridLayout(1,2));

1.

String  s[]={"11111","22222","33333","44444","55555",

"66666666","77777","888","9999999"};

JList  list1=new JList(s);

con.add(new JScrollPane(list1));

//2

Vector  v=new Vector();//向量----可变长度的数组

v.addElement("aaaaaaaa");

v.addElement("bbbba");

v.addElement("ccccccccc");

v.addElement("ddddddd");

v.addElement("aaaaaaaa");

v.addElement("bbbba");

v.addElement("ccccccccc");

v.addElement("ddddddd");

JList  list2=new JList(v);

con.add(new JScrollPane(list2));

f.setSize(400,300);

f.setVisible(true);

}

public static void main(String args[]) {

new Eg_1();

}

}

2设计一个库存查询窗口，要求能够在选择商品种类的同时，在窗口中显示该商品的价格和数量。商品有"色拉油","齐心汽水","米酒","冰淇淋","蛋糕"，相对应的价格和数量是：{"56"、"8"、"10"、"20"、"90"}，{"232"、"50"、"109"、"48"、"30"}。

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import java.util.Vector;

public class Eg_2 extends JApplet implements ItemListener{

//声明类，因为是小应用程序，故需要继承父类JApplet，并声明接口

Container ctp;

//容器

JTextField      tf1;

JTextField      tf2=new JTextField(5);//创建两个文本框类实例tf1

JLabel lb1=new JLabel("单价："),

lb2=new JLabel("库存量：");//创建两个标签类实例tf2

String      obj[]={"色拉油","齐心汽水","米酒","冰淇淋","蛋糕"},//定义三个数组，并付初始值

price[]={"56","8","10","20","90"},

num[]={"232","50","109","48","30"};

JComboBox cbx=new JComboBox();     //创建弹出式列表实例cbx

public void init(){                //写小应用程序的初始化方法init()

ctp=this.getContentPane();

ctp.setLayout(new FlowLayout());   //设置布局管理器-流布局管理器

tf1=new JTextField(5);

for(int n=0;n

cbx.addItem(obj[n]);

ctp.add(cbx);

cbx.addItemListener(this);          //为cbx安装监视器，this是指类自己本身

ctp.add(lb1);

ctp.add(tf1);

ctp.add(lb2);

ctp.add(tf2);

} //将标签、文本框、加到内容面板上

public void itemStateChanged(ItemEvent e){

int x=0,y;

String ko=(String)e.getItem();

for(y=0;y

if(ko==obj[y])

x=cbx.getSelectedIndex();

tf1.setText(price[x]);

tf2.setText(num[x]);

}

}

3 请你为单位设计一个“图书资料借用系统”。系统要求：借用图书资料的科室人员必须详细填写职工编号、图书资料名称、借书日期、还书日期、备注。(该例题形式常在网络问卷或会员注册中见到)。

import javax.swing.*;

import javax.swing.border.*;

import java.awt.*;

import java.awt.event.*;

public class Eg_3 implements ActionListener{

JFrame f = null;

Exercises 1.4Fill in the blanks in each of the following statements: a) The logical unit that receives information from outside thecomputer for use by thecomputer is theinput unit. b) The process of instructing the computer to solve a probl

public void actionPerformed(ActionEvent e) {  //实现ActionListener类接口的方法

String cls = e.getActionCommand(); //获得事件按钮的内容赋给字符串变量cls

//得到按钮上的名称

if (cls.equals("借阅图书资料")) {  //将cls的内容与字符串"借阅图书资料"比较

new LendingSystem(f);  //如果相同，就创建LendingSystem类的匿名实例

}

else if (cls.equals("关闭系统")) {  //否则就关闭系统窗口

System.exit(0);

}

}

public Eg_3(){    // 构建BookdataDialog类的构造方法

f = new JFrame("图书资料借阅系统");

Container contentPane = f.getContentPane();

JPanel buttonPanel = new JPanel();

JButton b = new JButton("借阅图书资料");

b.addActionListener(this);  //为按钮实例b安装监视器

buttonPanel.add(b);       //将按钮实例b加到面板容器中

b = new JButton("关闭系统");

b.addActionListener(this);

buttonPanel.add(b);

buttonPanel.setBorder(BorderFactory.createTitledBorder(BorderFactory.createLineBorder(Color.red,8),

"图书资料借阅系统",TitledBorder.CENTER,TitledBorder.TOP));

contentPane.add(buttonPanel,BorderLayout.CENTER);

f.pack();

f.setVisible(true);

}

public static void main(String[] args){

new Eg_3();

}

}

class LendingSystem implements ActionListener{  //声明LendingSystem类和接口

JTextField staffField,

objectField,

borrowDateField,

returnDateField,

reasonField;

JDialog dialog; //声明对话框对象

public void actionPerformed(ActionEvent e) {  //实现接口的方法

String cmd = e.getActionCommand();

if (cmd.equals("确定")) { }

else if(cmd.equals("取消")){

dialog.dispose();

}}

LendingSystem(JFrame f){     // 实现LendingSystem类的构造方法

dialog = new JDialog(f,"借用图书资料",false);  //创建对话框实例

GridBagConstraints c;     //创建容器对象c

//往袋布局限制类

int gridx,gridy,//网格坐标

gridwidth,gridheight,//所占网格的个数

anchor,//锚点

fill,//填充

ipadx,ipady;//定义整型数据变量

double weightx,weighty;   //是否可以放大---------不为0

Insets inset;             //创件插件类对象

GridBagLayout gridbag = new GridBagLayout(); //创建网袋布局管理器实例

Container dialogPane = dialog.getContentPane();

dialogPane.setLayout(gridbag);

///L1

JLabel label = new JLabel("图书资料编号 : "); //创建标签实例

gridx=0;               //第0列

gridy=0;               //第0行

gridwidth = 1;         //占一个单位宽度

gridheight = 1;        //占一个单位高度

weightx = 0;           //窗口增大时组件宽度增大比率0

weighty = 0;           //窗口增大时组件高度增大比率0

anchor = GridBagConstraints.CENTER; //容器大于组件size时将组件置于容器中央

fill = GridBagConstraints.BOTH;     //窗口拉大时会填满水平与垂直空间

inset = new Insets(0,0,0,0);        //组件间间距

ipadx = 0;                          //组件内水平宽度

ipady = 0;                          //组件内垂直高度

c = new GridBagConstraints(gridx,gridy,gridwidth,gridheight,

weightx,weighty,anchor,fill,inset,ipadx,ipady);

gridbag.setConstraints(label,c);

dialogPane.add(label);

///L2

label = new JLabel("图书资料名称 : ");

gridx=3;

gridy=0;

c = new GridBagConstraints(gridx,gridy,gridwidth,gridheight,

weightx,weighty,anchor,fill,inset,ipadx,ipady);

gridbag.setConstraints(label,c);

dialogPane.add(label);

L3