第四周作业
本人姓名：邹丰蔚
本人学号：201771010138
《面向对象程序设计（java）》第四周学习总结
1、实验目的与要求
(1) 理解用户自定义类的定义；
(2) 掌握对象的声明；
(3) 学会使用构造函数初始化对象；
(4) 使用类属性与方法的使用掌握使用；
(5) 掌握package和import语句的用途
2、实验内容和步骤
实验1 测试以下程序，掌握文件输入输出程序设计技术（文件输入输出，教材61-62）.
。
结果
实验2 导入第4章示例程序并测试。
import java.time.*;
public class CalendarTest
{
public static void main(String[] args)
{
LocalDate date=LocalDate.now();
int month=date.getMonthValue();
int today=date.getDayOfMonth();
date=date.minusDays(today-1);//Set to start of month
DayOfWeek weekday=date.getDayOfWeek();
int value=weekday.getValue();//1=Monday,...7=Sunday
System.out.println("Mon Tue Wed Thu Fri Sat Sun");
for(int i=1;i<value;i++)
System.out.print(" ");
while(date.getMonthValue()==month)
{
System.out.printf("%3d",date.getDayOfMonth());
if(date.getDayOfMonth()==today)
System.out.print("*");
else
System.out.print(" ");
date=date.plusDays(1);
if(date.getDayOfWeek().getValue()==1)System.out.println();
}
if(date.getDayOfWeek().getValue()!=1)System.out.println();
}
}
结果
l 编辑、编译、调试运行程序4-2（教材104页）；
l 结合程序运行结果，掌握类的定义与类对象的用法，并在程序代码中添加类与对象知识应用的注释；
l 尝试在项目中编辑两个类文件（Employee.java、 EmployeeTest.java ），编译并运行程序。
l 参考教材104页EmployeeTest.java，设计StudentTest.java，定义Student类，包含name（姓名）、sex（性别）、javascore（java成绩）三个字段，编写程序，从键盘输入学生人数，输入学生信息，并按以下表头输出学生信息表：
姓名 性别 java成绩
import java.time.*;
/**
* This program tests the Employee class.
* @version 1.12 2015-05-08
* @author Cay Horstmann
*/
public class EmployeeTest
{
public static void main(String[] args)
{
// fill the staff array with three Employee objects
Employee[] staff = new Employee[3];
staff[0] = new Employee("Carl Cracker", 75000, 1987, 12, 15);
staff[1] = new Employee("Harry Hacker", 50000, 1989, 10, 1);
staff[2] = new Employee("Tony Tester", 40000, 1990, 3, 15);
// raise everyone's salary by 5%
for (Employee e : staff)
e.raiseSalary(5);
// print out information about all Employee objects
for (Employee e : staff)
System.out.println("name=" + e.getName() + ",salary=" + e.getSalary() + ",hireDay="
+ e.getHireDay());
}
}
class Employee
{
private String name;
private double salary;
private LocalDate hireDay;
public Employee(String n, double s, int year, int month, int day)
{
name = n;
salary = s;
hireDay = LocalDate.of(year, month, day);
}
public String getName()
{
return name;
}
public double getSalary()
{
return salary;
}
public LocalDate getHireDay()
{
return hireDay;
}
public void raiseSalary(double byPercent)
{
double raise = salary * byPercent / 100;
salary += raise;
}
}
结果
（试验）学生
import java.time.*;
import java.util.Scanner;
public class StudentTest
{
public static void main(String[] args)
{
// fill the staff array with three Student objects
Employee[] staff = new Employee[4];
System.out.println("请输入学生：");
@SuppressWarnings("resource")
Scanner in = new Scanner(System.in);
for(int i=0;i<staff.length;i++) {
staff[i]=new Employee(in.next(),in.next(),in.nextInt());
}
System.out.println("name"+" "+"sex"+" "+" "+"javascore");
for (Employee e : staff)
System.out.println(e.getName() +" "+e.getSex()+" "+e.getJavaScore());
}
}
class Employee
{
private String name;
private String sex;
private int javascore;
public Employee(String n, String s, int m)
{
name = n;
sex = s;
javascore =m;
}
public String getName()
{
return name;
}
public String getSex()
{
return sex;
}
public int getJavaScore()
{
return javascore;
}
}
结果
测试程序2：
l 编辑、编译、调试运行程序4-3（教材116）；
l 结合程序运行结果，理解程序代码，掌握静态域（netxtId）与静态方法（getNextId）的用法，在相关代码后添加注释；
理解Java单元（类）测试的技巧。
/**
* This program demonstrates static methods.
* @version 1.01 2004-02-19
* @author Cay Horstmann
*/
public class StaticTest
{
public static void main(String[] args)
{
// fill the staff array with three Employee objects
Employee[] staff = new Employee[3];
staff[0] = new Employee("Tom", 40000);
staff[1] = new Employee("Dick", 60000);
staff[2] = new Employee("Harry", 65000);
// print out information about all Employee objects
for (Employee e : staff)
{
e.setId();
System.out.println("name=" + e.getName() + ",id=" + e.getId() + ",salary="
+ e.getSalary());
}
int n = Employee.getNextId(); // calls static method
System.out.println("Next available id=" + n);
}
}
class Employee
{
private static int nextId = 1;
private String name;
private double salary;
private int id;
public Employee(String n, double s)
{
name = n;
salary = s;
id = 0;
}
public String getName()
{
return name;
}
public double getSalary()
{
return salary;
}
public int getId()
{
return id;
}
public void setId()
{
id = nextId; // set id to next available id
nextId++;
}
public static int getNextId()
{
return nextId; // returns static field
}
public static void main(String[] args) // unit test
{
Employee e = new Employee("Harry", 50000);
System.out.println(e.getName() + " " + e.getSalary());
}
}
结果
测试程序3：
l 编辑、编译、调试运行程序4-4（教材121）；
l 结合程序运行结果，理解程序代码，掌握掌握Java方法参数的用法，在相关代码后添加注释；
/**
* This program demonstrates parameter passing in Java.
* @version 1.00 2000-01-27
* @author Cay Horstmann
*/
public class ParamTest
{
public static void main(String[] args)
{
/*
* Test 1: Methods can't modify numeric parameters
*/
System.out.println("Testing tripleValue:");
double percent = 10;
System.out.println("Before: percent=" + percent);
tripleValue(percent);
System.out.println("After: percent=" + percent);
/*
* Test 2: Methods can change the state of object parameters
*/
System.out.println("\nTesting tripleSalary:");
Employee harry = new Employee("Harry", 50000);
System.out.println("Before: salary=" + harry.getSalary());
tripleSalary(harry);
System.out.println("After: salary=" + harry.getSalary());
/*
* Test 3: Methods can't attach new objects to object parameters
*/
System.out.println("\nTesting swap:");
Employee a = new Employee("Alice", 70000);
Employee b = new Employee("Bob", 60000);
System.out.println("Before: a=" + a.getName());
System.out.println("Before: b=" + b.getName());
swap(a, b);
System.out.println("After: a=" + a.getName());
System.out.println("After: b=" + b.getName());
}
public static void tripleValue(double x) // doesn't work
{
x = 3 * x;
System.out.println("End of method: x=" + x);
}
public static void tripleSalary(Employee x) // works
{
x.raiseSalary(200);
System.out.println("End of method: salary=" + x.getSalary());
}
public static void swap(Employee x, Employee y)
{
Employee temp = x;
x = y;
y = temp;
System.out.println("End of method: x=" + x.getName());
System.out.println("End of method: y=" + y.getName());
}
}
class Employee // simplified Employee class
{
private String name;
private double salary;
public Employee(String n, double s)
{
name = n;
salary = s;
}
public String getName()
{
return name;
}
public double getSalary()
{
return salary;
}
public void raiseSalary(double byPercent)
{
double raise = salary * byPercent / 100;
salary += raise;
}
}
结果
测试程序4：
l 编辑、编译、调试运行程序4-5（教材129）；
l 结合程序运行结果，理解程序代码，掌握Java用户自定义类的用法，掌握对象构造方法及对象使用方法，在相关代码后添加注释。
import java.util.*;
/**
* This program demonstrates object construction.
* @version 1.01 2004-02-19
* @author Cay Horstmann
*/
public class ConstructorTest
{
public static void main(String[] args)
{
// fill the staff array with three Employee objects
Employee[] staff = new Employee[3];
staff[0] = new Employee("Harry", 40000);
staff[1] = new Employee(60000);
staff[2] = new Employee();
// print out information about all Employee objects
for (Employee e : staff)
System.out.println("name=" + e.getName() + ",id=" + e.getId() + ",salary="
+ e.getSalary());
}
}
class Employee
{
private static int nextId;
private int id;
private String name = ""; // instance field initialization
private double salary;
// static initialization block
static
{
Random generator = new Random();
// set nextId to a random number between 0 and 9999
nextId = generator.nextInt(10000);
}
// object initialization block
{
id = nextId;
nextId++;
}
// three overloaded constructors
public Employee(String n, double s)
{
name = n;
salary = s;
}
public Employee(double s)
{
// calls the Employee(String, double) constructor
this("Employee #" + nextId, s);
}
// the default constructor
public Employee()
{
// name initialized to ""--see above
// salary not explicitly set--initialized to 0
// id initialized in initialization block
}
public void Employee1() {
// TODO Auto-generated constructor stub
}
public String getName()
{
return name;
}
public double getSalary()
{
return salary;
}
public int getId()
{
return id;
}
}
结果
测试程序5：
l 编辑、编译、调试运行程序4-6、4-7（教材135）；
l 结合程序运行结果，理解程序代码，掌握Java包的定义及用法，在相关代码后添加注释；
import static java.lang.System.*;
/**
* This program demonstrates the use of packages.
* @version 1.11 2004-02-19
* @author Cay Horstmann
*/
public class PackageTest
{
public static void main(String[] args)
{
// because of the import statement, we don't have to use
// com.horstmann.corejava.Employee here
Employee harry = new Employee("Harry Hacker", 50000, 1989, 10, 1);
harry.raiseSalary(5);
// because of the static import statement, we don't have to use System.out here
out.println("name=" + harry.getName() + ",salary=" + harry.getSalary());
}
}
结果
实验3 编写长方形类Rectangle与圆形类Circle，其中Rectangle类设置私有属性：width,length；Circle类设置私有属性radius。编写Rectangle类的带参构造函数Rectangle(int width,int length), Circle类的带参构造函数Circle(int radius)，编写两个类的toString方法(Eclipse可自动生成)。上述2个类均定义以下方法：
求周长的方法public int getPerimeter()
求面积的方法public int getArea()
在main方法中完成以下任务：
（1） 输入1行长与宽，创建一个Rectangle对象；
（2） 输入1行半径，创建一个Circle对象；
（3） 将两个对象的周长加总输出，将两个对象的面积加总输出。
import java.util.Scanner;
public class shiyan{
public static void main(String[] args) {
// TODO 自动生成的方法存根
final float PI=3.14f;
System.out.println("请输入长方形的长:");
System.out.println("请输入长方形的宽:");
System.out.println("请输入圆的半径:");
@SuppressWarnings("resource")
Scanner sc=new Scanner(System.in);
int a1=sc.nextInt();
int b1 = sc.nextInt();
int r = sc.nextInt();
int area1=a1*b1;
float area2 = PI*r*r;
int perimeter1 = (int) (2*(a1+b1));
float perimeter2= 2*PI*r;
System.out.println("长方形的面积:"+area1);
System.out.println("长方形的周长:"+perimeter1);
System.out.println("圆的面积是:"+area2);
System.out.println("圆的周长是:"+perimeter2);
}
}
总结：通过这个周的学习，我认识了什么是类，什么是对象,并了解了对象的三个特征：行为，状态，对象标识。掌握了package和import语句的用途。也熟悉Math类、String类、math类、Scanner类、LocalDate类的常用API。通过本章的学习我认识到了自己的不足，也学到了很多东西。