第二课

栗子1
这一个测试了关于不同包的新建和引用问题。(一个是默认包，一个是新建的测试包)

//---------------------------Employee.java

package com.f.corajava;

import java.util.*;

public class Employee 
{
    private String name;
    private double salary;
    private Date hireday;

    public Employee(String n,double s,int year,int month,int day)
    {
        name=n;
        salary=s;
        GregorianCalendar calendar=new GregorianCalendar(year,month-1,day);
        hireday=calendar.getTime();     
    }

    public String getName()
    {
        return name;
    }
    public double getSalary()
    {
        return salary;
    }
    public Date getHireday()
    {
        return hireday;
    }
    public void raiseSalary(double byPercent)
    {
        double raise=salary*byPercent;
        salary+=raise;      
    }
}

//--------------------------PackageTest.java

import com.f.corajava.*;    //导入定义Employee类那个包
import static java.lang.System.*;   //静态导入类文件时，在下面的引用方法时可不加类名前缀

public class PackageTest 
{
    /**
     * @param args
     */
    public static void main(String[] args) 
    {
        // TODO Auto-generated method stub
        Employee[] staff=new Employee[2];   //声明对象数组,以及下面对两个数组对象成员定义时都得用new
        staff[0]= new Employee("Tom",7500,1987,12,15);
        staff[1]=new Employee("Jack",10000,1985,06,03);

        out.println("Before:");
        for(Employee e:staff)
            out.println("name="+e.getName()+"---salary="+e.getSalary()+"---hireday="+e.getHireday());

        out.println("After:");
        Employee Jack=staff[1];
        Jack.raiseSalary(10);
        out.println("name="+Jack.getName()+"---salary="+Jack.getSalary());      
    }
}

结果：

注1：关于对Java.util包，其基本层次结构如下：
摘自：http://blog.youkuaiyun.com/abeetle/article/details/1497706

栗子2：关于枚举类

//-------------------------Size.java
package enums;

public enum Size //定义一个枚举类（型号）
{
    //列出所有的枚举常量
    SMALL("S"),MEDIUM("M"),LARGE("L"),EXTRA_LARGE("XL");
    //添加域、构造器和其他方法
    private String abbreviation;
    private Size(String abbreviation){this.abbreviation=abbreviation;}
    public String getAbbreviation() {return abbreviation;}  
}

//--------------------------------EnumTest.java
package enums;
import java.util.*;
public class EnumTest 
{
    /**
     * @param args
     */
    public static void main(String[] args) 
    {
        // TODO Auto-generated method stub
        Scanner in=new Scanner(System.in);
        System.out.print("Enter a size:(SMALL,MEDIUM,LARGE,EXTRA_LARGE)");
        //toUpperCase()将所输入的英文字母小写转换成大写的，相反的是toLowerCase()
        String input =in.next().toUpperCase();
        /****************************************************
        toString()可以返回枚举常量名,如Size.SMALL.toString()返回字符串"SMALL"
        相反的操作便是valueOf()
        Size s=Enum.valueOf(Size.class,"SMALL");表示将s设置成Size.SMALL
        ****************************************************/
        Size s=Enum.valueOf(Size.class, input);
        System.out.println("size="+s);
        //这个getAbbreviation()是什么意思？他为什么能够返回L?
        System.out.println("abbreviation="+s.getAbbreviation());
        if(s==Size.EXTRA_LARGE)
            System.out.println("Good job--you paid attention to the _.");
    }

}

结果：