张季跃 201771010139《面向对象程序设计(java)》第八周学习总结
理论知识部分:
6.1 接口
l(1)Java为了克服单继承的缺点,Java使用了接口, 一个类可以实现一个或多个接口。 l
(2) 在Java程序设计语言中,接口不是类,而是对类 的一组需求描述,由常量和一组抽象方法组成。 l
(3) 接口中不包括变量和有具体实现的方法。 l
(4) 只要类实现了接口,则该类要遵从接口描述的统 一格式进行定义,并且可以在任何需要该接口的 地方使用这个类的对象.
6.2 接口示例
l(1)接口与回调
la.回调(callback):一种程序设计模式,在这种模 式中,可指出某个特定事件发生时程序应该采取 的动作。 l
B.在java.swing包中有一个Timer类,可以使用它 在到达给定的时间间隔时触发一个事件。
l(2)Comparator接口
la.所在包:java.util.* l
b.Comparator接口定义
lc.用途一:处理字符串按长度进行排序的操作
(3)对象克隆
la.Object类的Clone方法
lb.浅层拷贝与深层拷贝
lc.Java中对象克隆的实现
6.3 lambda表达式
lJava Lambda 表达式是Java 8 引入的一个新的功能,主 要用途是提供一个函数化的语法来简化编码
1、实验目的与要求
(1) 掌握接口定义方法;
(2) 掌握实现接口类的定义要求;
(3) 掌握实现了接口类的使用要求;
(4) 掌握程序回调设计模式;
(5) 掌握Comparator接口用法;
(6) 掌握对象浅层拷贝与深层拷贝方法;
(7) 掌握Lambda表达式语法;
(8) 了解内部类的用途及语法要求。
2、实验内容和步骤
实验1: 导入第6章示例程序,测试程序并进行代码注释。
测试程序1:
l 编辑、编译、调试运行阅读教材214页-215页程序6-1、6-2,理解程序并分析程序运行结果;
l 在程序中相关代码处添加新知识的注释。
l 掌握接口的实现用法;
l 掌握内置接口Compareable的用法。
实验代码:
package interfaces;
import java.util.*;
/**
* This program demonstrates the use of the Comparable interface.
* @version 1.30 2004-02-27
* @author Cay Horstmann
*/
public class EmployeeSortTest
{
public static void main(String[] args)
{
Employee[] staff = new Employee[3];
staff[0] = new Employee("Harry Hacker", 35000);
staff[1] = new Employee("Carl Cracker", 75000);
staff[2] = new Employee("Tony Tester", 38000);
Arrays.sort(staff);
//输出所有关于Employee对象的信息
for (Employee e : staff)
System.out.println("name=" + e.getName() + ",salary=" + e.getSalary());
}
}
package interfaces;
public class Employee implements Comparable<Employee>
//创建一个泛型Comparable接口,提供一个类型参数,比较Employee类的对象并进行排序
{
private String name;
private double salary;
public Employee(String name, double salary)
{
this.name = name;
this.salary = salary;
}
public String getName()
{
return name;
}
public double getSalary()
{
return salary;
}
public void raiseSalary(double byPercent)
{
double raise = salary * byPercent / 100;
salary += raise;
}
/**
* Compares employees by salary
* @param other another Employee object
* @return a negative value if this employee has a lower salary than
* otherObject, 0 if the salaries are the same, a positive value otherwise
*/
public int compareTo(Employee other)
{
return Double.compare(salary, other.salary);
//salary的大小两两互相比较,升序排出salary的大小
}
}
实验结果:
测试程序2:
l 编辑、编译、调试以下程序,结合程序运行结果理解程序;
interface A { double g=9.8; void show( ); } class C implements A { public void show( ) {System.out.println("g="+g);} }
class InterfaceTest { public static void main(String[ ] args) { A a=new C( ); a.show( ); System.out.println("g="+C.g); } } |
实验结果:
测试程序3:
l 在elipse IDE中调试运行教材223页6-3,结合程序运行结果理解程序;
l 26行、36行代码参阅224页,详细内容涉及教材12章。
l 在程序中相关代码处添加新知识的注释。
l 掌握回调程序设计模式;
实验程序:
interface A
{
double g=9.8;
void show( );
}
class C implements A
{
public void show( )
{System.out.println("g="+g);}
}
class InterfaceTest
{
public static void main(String[ ] args)
{
A a=new C( );
a.show( );
System.out.println("g="+C.g);
}
}
实验结果:
测试程序4:
l 调试运行教材229页-231页程序6-4、6-5,结合程序运行结果理解程序;
l 在程序中相关代码处添加新知识的注释。
l 掌握对象克隆实现技术;
l 掌握浅拷贝和深拷贝的差别。
实验程序:
package clone;
/**
* This program demonstrates cloning.
* @version 1.10 2002-07-01
* @author Cay Horstmann
*/
public class CloneTest
{
public static void main(String[] args)
{
try
{
Employee original = new Employee("John Q. Public", 50000);
//Employee是一个自定义类
original.setHireDay(2000, 1, 1);
Employee copy = original.clone();
copy.raiseSalary(10);//原有对象不会发生变化
copy.setHireDay(2002, 12, 31);//更改器
System.out.println("original=" + original);//字符串连接
System.out.println("copy=" + copy);
}
catch (CloneNotSupportedException e)
{
e.printStackTrace();
}
}
}
实验结果:
实验2: 导入第6章示例程序6-6,学习Lambda表达式用法。
l 调试运行教材233页-234页程序6-6,结合程序运行结果理解程序;
l 在程序中相关代码处添加新知识的注释。
l 将27-29行代码与教材223页程序对比,将27-29行代码与此程序对比,体会Lambda表达式的优点。
实验程序:
package lambda;
import java.util.*;
import javax.swing.*;
import javax.swing.Timer;
/**
* This program demonstrates the use of lambda expressions.
* @version 1.0 2015-05-12
* @author Cay Horstmann
*/
public class LambdaTest
{
public static void main(String[] args)
{
String[] planets = new String[] { "Mercury", "Venus", "Earth", "Mars",
"Jupiter", "Saturn", "Uranus", "Neptune" };//定义数组planets
System.out.println(Arrays.toString(planets));//静态方法
System.out.println("Sorted in dictionary order:");
Arrays.sort(planets);//Arrays.sort方法接收实验Lambda类的对象
System.out.println(Arrays.toString(planets));
System.out.println("Sorted by length:");
Arrays.sort(planets, (first, second) -> first.length() - second.length());//Lambda表达式
System.out.println(Arrays.toString(planets));
Timer t = new Timer(1000, event ->
System.out.println("The time is " + new Date()));//Lambda表达式
t.start();
// keep program running until user selects "Ok"
JOptionPane.showMessageDialog(null, "Quit program?");
System.exit(0); //返回类型
}
}
package clone;
import java.util.Date;
import java.util.GregorianCalendar;
public class Employee implements Cloneable
{
//定义三个私有属性
private String name;//string类在lang包
private double salary;
private Date hireDay;
public Employee(String name, double salary)
{
this.name = name;
this.salary = salary;
hireDay = new Date();
}//构造方法
public Employee clone() throws CloneNotSupportedException
{
// call Object.clone()
Employee cloned = (Employee) super.clone();//强制类型转换
// clone mutable fields
cloned.hireDay = (Date) hireDay.clone();
return cloned;
}
/**
* Set the hire day to a given date.
* @param year the year of the hire day
* @param month the month of the hire day
* @param day the day of the hire day
*/
public void setHireDay(int year, int month, int day)
{
Date newHireDay = new GregorianCalendar(year, month - 1, day).getTime();
//创建一个实例字段变异的实例
// Example of instance field mutation
hireDay.setTime(newHireDay.getTime());
}
public void raiseSalary(double byPercent)
{
double raise = salary * byPercent / 100;
salary += raise;
}//调用
public String toString()
{
return "Employee[name=" + name + ",salary=" + salary + ",hireDay=" + hireDay + "]";
}
}
实验结果:
注:以下实验课后完成
实验3: 编程练习
l 编制一个程序,将身份证号.txt 中的信息读入到内存中;
l 按姓名字典序输出人员信息;
l 查询最大年龄的人员信息;
l 查询最小年龄人员信息;
l 输入你的年龄,查询身份证号.txt中年龄与你最近人的姓名、身份证号、年龄、性别和出生地;
l 查询人员中是否有你的同乡。
实验程序:
package shen;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Scanner;
public class Main{
private static ArrayList<Student> studentlist;
public static void main(String[] args) {
studentlist = new ArrayList<>();
Scanner scanner = new Scanner(System.in);
File file = new File("C:\\Users\\ASUS\\Desktop\\新建文件夹\\身份证号.txt");
try {
FileInputStream fis = new FileInputStream(file);
BufferedReader in = new BufferedReader(new InputStreamReader(fis));
String temp = null;
while ((temp = in.readLine()) != null) {
Scanner linescanner = new Scanner(temp);
linescanner.useDelimiter(" ");
String name = linescanner.next();
String number = linescanner.next();
String sex = linescanner.next();
String age = linescanner.next();
String province =linescanner.nextLine();
Student student = new Student();
student.setName(name);
student.setnumber(number);
student.setsex(sex);
int a = Integer.parseInt(age);
student.setage(a);
student.setprovince(province);
studentlist.add(student);
}
} catch (FileNotFoundException e) {
System.out.println("学生信息文件找不到");
e.printStackTrace();
} catch (IOException e) {
System.out.println("学生信息文件读取错误");
e.printStackTrace();
}
boolean isTrue = true;
while (isTrue) {
System.out.println("选择你的操作,输入正确格式的选项");
System.out.println("A.字典排序");
System.out.println("B.输出年龄最大和年龄最小的人");
System.out.println("C.寻找老乡");
System.out.println("D.寻找年龄相近的人");
System.out.println("F.退出");
String m = scanner.next();
switch (m) {
case "A":
Collections.sort(studentlist);
System.out.println(studentlist.toString());
break;
case "B":
int max=0,min=100;
int j,k1 = 0,k2=0;
for(int i=1;i<studentlist.size();i++)
{
j=studentlist.get(i).getage();
if(j>max)
{
max=j;
k1=i;
}
if(j<min)
{
min=j;
k2=i;
}
}
System.out.println("年龄最大:"+studentlist.get(k1));
System.out.println("年龄最小:"+studentlist.get(k2));
break;
case "C":
System.out.println("老家?");
String find = scanner.next();
String place=find.substring(0,3);
for (int i = 0; i <studentlist.size(); i++)
{
if(studentlist.get(i).getprovince().substring(1,4).equals(place))
System.out.println("老乡"+studentlist.get(i));
}
break;
case "D":
System.out.println("年龄:");
int yourage = scanner.nextInt();
int near=agenear(yourage);
int value=yourage-studentlist.get(near).getage();
System.out.println(""+studentlist.get(near));
break;
case "F":
isTrue = false;
System.out.println("退出程序!");
break;
default:
System.out.println("输入有误");
}
}
}
public static int agenear(int age) {
int j=0,min=53,value=0,k=0;
for (int i = 0; i < studentlist.size(); i++)
{
value=studentlist.get(i).getage()-age;
if(value<0) value=-value;
if (value<min)
{
min=value;
k=i;
}
}
return k;
}
}
Main
package shen;
public class Student implements Comparable<Student> {
private String name;
private String number ;
private String sex ;
private int age;
private String province;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getnumber() {
return number;
}
public void setnumber(String number) {
this.number = number;
}
public String getsex() {
return sex ;
}
public void setsex(String sex ) {
this.sex =sex ;
}
public int getage() {
return age;
}
public void setage(int age) {
// int a = Integer.parseInt(age);
this.age= age;
}
public String getprovince() {
return province;
}
public void setprovince(String province) {
this.province=province ;
}
public int compareTo(Student o) {
return this.name.compareTo(o.getName());
}
public String toString() {
return name+"\t"+sex+"\t"+age+"\t"+number+"\t"+province+"\n";
}
}
实验结果
l 编辑、调试运行教材246页-247页程序6-7,结合程序运行结果理解程序;
l 了解内部类的基本用法。
实验程序:
package innerClass;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import javax.swing.Timer;
/**
* This program demonstrates the use of inner classes.
* @version 1.11 2015-05-12
* @author Cay Horstmann
*/
public class InnerClassTest
{
public static void main(String[] args)
{
TalkingClock clock = new TalkingClock(1000, true);
clock.start();
// keep program running until user selects "Ok"
JOptionPane.showMessageDialog(null, "Quit program?");
System.exit(0);
}
}
/**
* A clock that prints the time in regular intervals.
*/
class TalkingClock
{
private int interval;
private boolean beep;
/**
* Constructs a talking clock
* @param interval the interval between messages (in milliseconds)
* @param beep true if the clock should beep
*/
public TalkingClock(int interval, boolean beep)
{
this.interval = interval;
this.beep = beep;
}
/**
* Starts the clock.
*/
public void start()
{
ActionListener listener = new TimePrinter();
Timer t = new Timer(interval, listener);
t.start();
}
public class TimePrinter implements ActionListener
{
public void actionPerformed(ActionEvent event)
{
System.out.println("At the tone, the time is " + new Date());
if (beep) Toolkit.getDefaultToolkit().beep();
}
}
}
实验结果:
实验程序2:
l 编辑、调试运行教材254页程序6-8,结合程序运行结果理解程序;
l 了解匿名内部类的用法。
实验程序:
package anonymousInnerClass;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import javax.swing.Timer;
/**
* This program demonstrates anonymous inner classes.
* @version 1.11 2015-05-12
* @author Cay Horstmann
*/
public class AnonymousInnerClassTest
{
public static void main(String[] args)
{
TalkingClock clock = new TalkingClock();
clock.start(1000, true);
// keep program running until user selects "Ok"
JOptionPane.showMessageDialog(null, "Quit program?");
System.exit(0);
}
}
/**
* A clock that prints the time in regular intervals.
*/
class TalkingClock
{
/**
* Starts the clock.
* @param interval the interval between messages (in milliseconds)
* @param beep true if the clock should beep
*/
public void start(int interval, boolean beep)
{
ActionListener listener = new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
System.out.println("At the tone, the time is " + new Date());
if (beep) Toolkit.getDefaultToolkit().beep();
}
};
Timer t = new Timer(interval, listener);
t.start();
}
}
实验结果:
实验程序3:
l 在elipse IDE中调试运行教材257页-258页程序6-9,结合程序运行结果理解程序;
l 了解静态内部类的用法。
实验程序:package staticInnerClass;
/**
* This program demonstrates the use of static inner classes.
* @version 1.02 2015-05-12
* @author Cay Horstmann
*/
public class StaticInnerClassTest
{
public static void main(String[] args)
{
double[] d = new double[20];
for (int i = 0; i < d.length; i++)
d[i] = 100 * Math.random();
ArrayAlg.Pair p = ArrayAlg.minmax(d);
System.out.println("min = " + p.getFirst());
System.out.println("max = " + p.getSecond());
}
}
class ArrayAlg
{
/**
* A pair of floating-point numbers
*/
public static class Pair
{
private double first;
private double second;
/**
* Constructs a pair from two floating-point numbers
* @param f the first number
* @param s the second number
*/
public Pair(double f, double s)
{
first = f;
second = s;
}
/**
* Returns the first number of the pair
* @return the first number
*/
public double getFirst()
{
return first;
}
/**
* Returns the second number of the pair
* @return the second number
*/
public double getSecond()
{
return second;
}
}
/**
* Computes both the minimum and the maximum of an array
* @param values an array of floating-point numbers
* @return a pair whose first element is the minimum and whose second element
* is the maximum
*/
public static Pair minmax(double[] values)
{
double min = Double.POSITIVE_INFINITY;
double max = Double.NEGATIVE_INFINITY;
for (double v : values)
{
if (min > v) min = v;
if (max < v) max = v;
}
return new Pair(min, max);
}
}
实验结果:
实验总结:
在本周的学习过程中,我第一次接触了接口的概念并对有关知识的应用有了初步的掌握。并且在学习过程中,我学习到了有关回调与对象克隆的知识。最后,我还对Lambda表达式有了初步的认识。但总体而言,我本周的学习并没有得到太大的成果,做实验报告时遇到了很多搞不懂东西,就算请教了同学也没有完全理解。
原文地址:https://www.cnblogs.com/Alex-Morcer/p/9825706.html