book类练习题

1、编写一个Book类，该类至少有name和price两个属性。该类要实现Comparable接口，在接口的compareTo（）方法中规定两个Book类实例的大小关系为二者的price属性的大小关系。在主函数中，选择合适的集合类型存放Book类的若干个对象，然后创建一个新的Book类的对象，并检查该对象与集合中的哪些对象相等。

代码如下：

import java.util.ArrayList;import java.util.Collections;import java.util.Iterator;import java.util.List;public class Book implements Comparable{    public String name;    public double price;    public Book(String name, double price) {        this.name = name;        this.price = price;    }    @SuppressWarnings("unchecked")    public static void main(String[] args) {        // TODO Auto-generated method stub        List<Book> booklist = new ArrayList<Book>();        Book b1 = new Book("java基础教程", 30.0);        Book b2 = new Book("C++基础教程", 28.0);        Book b3 = new Book("数据库技术", 29.0);        Book b4 = new Book("计算机网络", 29.0);        Book b5 = new Book("高等数学", 29.0);        booklist.add(b1);        booklist.add(b2);        booklist.add(b3);        booklist.add(b4);        booklist.add(b5);        Book b6 = new Book("模式识别", 29.0);        System.out.println("新书《" + b6.name + "》与下列图书:");        for (int i = 0; i < booklist.size(); i++) {            Book book = (Book) booklist.get(i);            int index = book.compareTo(b4);            if (index == 0) {                System.out.print("《"+book.name);                System.out.println("》");            }        }        System.out.print("相同" + "具体价格为" + b4.price + "元");    }    public int compareTo(Object obj) {        Book p = (Book) obj;        return (int) (p.price-this.price);    }}

运行结果：

2、编写一个应用程序，用户分别从两个文本框输入学术的姓名和分数，程序按成绩排序将这些学生的姓名和分数显示在一个文本区中。

代码如下：

import java.awt.FlowLayout;import java.awt.Label;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.util.ArrayList;import java.util.Collections;import java.util.Iterator;import java.util.List;import javax.swing.Box;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JTextArea;import javax.swing.JTextField;public class ScoreOrder extends JFrame implements ActionListener {    JFrame jframe;    JTextField jtextfield1;    JTextField jtextfield2;    JTextArea jtextarea;    List<Student> list = new ArrayList<Student>();    public static void main(String[] args) {        // TODO Auto-generated method stub        ScoreOrder myJframe = new ScoreOrder();// 显示窗口    }    ScoreOrder() {        jframe = new JFrame("成绩排序");        jframe.setBounds(200, 100, 700, 400);        jframe.setLayout(new FlowLayout());        jtextfield1 = new JTextField(10);        jtextfield2 = new JTextField(10);        JButton jbutton = new JButton("插入");        Box box = Box.createHorizontalBox();        box.add(new Label("姓名:"));        box.add(jtextfield1);        box.add(new Label("分数:"));        box.add(jtextfield2);        box.add(Box.createHorizontalStrut(50));        box.add(jbutton);        jframe.add(box);        jtextarea = new JTextArea(40, 80);        jframe.add(jtextarea);        jframe.setVisible(true);        jbutton.addActionListener(this);    }    @Override    public void actionPerformed(ActionEvent e) {        // TODO Auto-generated method stub        jtextarea.setText("");        String name = jtextfield1.getText();        String grade = jtextfield2.getText();        if (!"".equals(name) && !"".equals(grade)) {            list.add(new Student(name, Float.parseFloat(grade)));            jtextarea.append("当前插入的信息为:姓名:" + name + "    成绩:" + grade + "\n");        }        Collections.sort(list);// 对list排序        Iterator<Student> iterator = list.iterator();        Student student;        while (iterator.hasNext()) {            student = iterator.next();            jtextarea.append("name:" + student.name + "    grade:" + student.grade + "\n");        }    }}class Student implements Comparable<Student> {    String name;    float grade;    public Student(String name, float grade) {        super();        this.name = name;        this.grade = grade;    }    @Override    public int compareTo(Student o) {        // TODO Auto-generated method stub        return (int) (o.grade - this.grade);    }}

运行结果：