BlogJava-搭上奋斗的班车-文章分类-J2SE练习册

ReflectionTest

搭上奋斗的班车 — Wed, 14 Jan 2009 16:02:00 GMT

import java.util.*;
import java.lang.reflect.*;

public class ReflectionTest
{
    public static void main(String[] args)
    {
        String name;
        if(args.length > 0)
            name = args[0];
        else
        {
            Scanner in = new Scanner(System.in);
            System.out.println("Enter class name (e.g. java.util.Date): ");
            name = in.next();
        }

        try
        {
            Class cl = Class.forName(name);
            Class supercl = cl.getSuperclass();
            System.out.print("class " + name);
            if(supercl != null && supercl != Object.class)
                System.out.print(" extends " + supercl.getName());

            System.out.print("\n{\n");
            printConstructors(cl);
            System.out.println();
            printMethods(cl);
            System.out.println();
            printFields(cl);
            System.out.println("}");
        }
        catch(ClassNotFoundException e){ e.printStackTrace();}
        System.exit(0);
    }

    public static void printConstructors(Class cl)
    {
        Constructor[] constructors = cl.getDeclaredConstructors();

        for(Constructor c : constructors)
        {
            String name = c.getName();
            System.out.print("   " + Modifier.toString(c.getModifiers()));
            System.out.print(" " + name + "(");

            Class[] paramTypes = c.getParameterTypes();
            for(int j = 0;j < paramTypes.length;j++)
            {
                if(j > 0) System.out.print(", ");
                System.out.print(paramTypes[j].getName());
            }
            System.out.println(");");
        }
    }

    public static void printMethods(Class cl)
    {
        Method[] methods = cl.getDeclaredMethods();

        for(Method m : methods)
        {
            Class retType = m.getReturnType();
            String name = m.getName();

            System.out.print("   " + Modifier.toString(m.getModifiers()));
            System.out.print(" " + retType.getName() + " " + name + "(");

            Class[] paramTypes = m.getParameterTypes();
            for(int j = 0;j < paramTypes.length;j++)
            {
                if(j > 0) System.out.print(", ");
                System.out.print(paramTypes[j].getName());
            }
            System.out.println(");");
        }
    }

    public static void printFields(Class cl)
    {
        Field[] fields = cl.getDeclaredFields();

        for(Field f : fields)
        {
            Class type = f.getType();
            String name = f.getName();
            System.out.print("   " + Modifier.toString(f.getModifiers()));
            System.out.println(" " + type.getName() + " " + name + ";");
        }
    }
}

搭上奋斗的班车 2009-01-15 00:02 发表评论

泛型数组列表 ArrayList

搭上奋斗的班车 — Wed, 14 Jan 2009 13:40:00 GMT

import java.util.*;

public class ArrayListTest
{
    public static void main(String[] args)
    {
        ArrayList<Employee> staff=new ArrayList<Employee>();

        staff.add(new Employee("Carl Cracker",75000,1987,12,15));
        staff.add(new Employee("Harry Hacker",50000,1989,10,1));
        staff.add(new Employee("Tony Tester",40000,1990,3,15));

        for(Employee e : staff)
            e.raiseSalary(5);

        for(Employee e : staff)
            System.out.println("name=" + e.getName()
            +",salary=" + e.getSalary()
            +",hireDay=" + e.getHireDay());
    }
}

class Employee
{
    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 / 100;
        salary += raise;
    }

    private String name;
    private double salary;
    private Date hireDay;
}

搭上奋斗的班车 2009-01-14 21:40 发表评论

equals，hashCode和toString方法

搭上奋斗的班车 — Tue, 13 Jan 2009 16:00:00 GMT

import java.util.*;

public class EqualsTest
{
    public static void main(String[] args)
    {
        Employee alice1=new Employee("Alice Adams",75000,1987,12,15);
        Employee alice2=alice1;
        Employee alice3=new Employee("Alice Adams",75000,1987,12,15);
        Employee bob=new Employee("Bob Brandson",50000,1989,10,1);

        System.out.println("alice1==alice2: " + (alice1 == alice2));
        System.out.println("alice1==alice3: " + (alice1==alice3));
        System.out.println("alice1.equals(alice3): " + alice1.equals(alice3));
        System.out.println("alice1.equals(bob): " + alice1.equals(bob));
        System.out.println("bob.toString(): " + bob);

        Manager carl=new Manager("Carl Cracker",80000,1987,12,15);
        Manager boss=new Manager("Carl Cracker",80000,1987,12,15);
        boss.setBonus(5000);
        System.out.println("boss.toString(): " + boss);
        System.out.println("carl.equals(boss): " + alice1.equals(boss));
        System.out.println("alice1.hashCode(): " + alice1.hashCode());
        System.out.println("alice3.hashCode(): " + alice3.hashCode());
        System.out.println("bob.hashCode(): " + bob.hashCode());
        System.out.println("carl.hashCode(): " + carl.hashCode());
    }
}

class Employee
{
    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 / 100;
        salary += raise;
    }

    public boolean equals(Object otherObject)
    {
        if(this == otherObject) return true;

        if(otherObject == null) return false;

        if(getClass() != otherObject.getClass())
            return false;

        Employee other = (Employee) otherObject;

        return name.equals(other.name)
        && salary == other.salary
        && hireDay.equals(other.hireDay);
    }

    public int hashCode()
    {
        return 7 * name.hashCode()
        + 11 * new Double(salary).hashCode()
        + 13 * hireDay.hashCode();
    }

    public String toString()
    {
        return getClass().getName()
        + "[name=" + name
        + ",salary=" + salary
        + ",hireDay=" + hireDay
        + "]";
    }

    private String name;
    private double salary;
    private Date hireDay;
}

class Manager extends Employee
{
    public Manager(String n,double s,int year,int month,int day)
    {
        super(n,s,year,month,day);
        bonus=0;
    }

    public double getSalary()
    {
        double baseSalary = super.getSalary();
        return baseSalary + bonus;
    }

    public void setBonus(double b)
    {
        bonus = b;
    }

    public boolean equals(Object otherObject)
    {
        if(!super.equals(otherObject)) return false;
        Manager other = (Manager) otherObject;

        return bonus == other.bonus;
    }

    public int hashCode()
    {
        return super.hashCode()
        + 17 * new Double(bonus).hashCode();
    }

    public String toString()
    {
        return super.toString()
        + "[bonus=" + bonus
        + "]";
    }

    private double bonus;
}

搭上奋斗的班车 2009-01-14 00:00 发表评论

抽象类

搭上奋斗的班车 — Tue, 13 Jan 2009 13:26:00 GMT

import java.text.*;
import java.util.*;

public class PersonTest
{
public static void main(String[] args)
{
  Person[] people=new Person[2];

  people[0]=new Employee("Harry Hacker",50000,1989,10,1);
  people[1]=new Student("Maria Morris","computer science");

  for(Person p:people)
   System.out.println(p.getName() + "," + p.getDescription());
}
}
abstract class Person
{
public Person(String n)
{
  name=n;
}

public abstract String getDescription();

public String getName()
{
  return name;
}
private String name;
}

class Employee extends Person
{
public Employee(String n,double s,int year,int month,int day)
{
  super(n);
  salary=s;
  GregorianCalendar calendar=new GregorianCalendar(year,month-1,day);
  hireDay=calendar.getTime();
}

public double getSalary()
{
  return salary;
}

public Date getHireDay()
{
  return hireDay;
}

public String getDescription()
{
  return String.format("an employee with a salary of 5%.2f",salary);
}

public void raiseSalary(double byPercent)
{
  double raise=salary * byPercent / 100;
  salary += raise;
}

private double salary;
private Date hireDay;
}

class Student extends Person
{
public Student(String n,String m)
{
  super(n);
  major=m;
}

public String getDescription()
{
  return "a student majoring in " + major;
}

private String major;
}

搭上奋斗的班车 2009-01-13 21:26 发表评论

无题.(小练习)

搭上奋斗的班车 — Sun, 11 Jan 2009 15:37:00 GMT

这个程序我用Eclipse运行有错误，用命令提示符就没问题。哎，不知怎么搞。

import java.util.GregorianCalendar;

public class ManagerTest
{
    public static void main(String[] args)
    {
        Manager boss=new Manager("Carl Cracker",80000,1987,12,15);
        boss.setBonus(5000);

        Employee[] staff=new Employee[3];

        staff[0]=boss;
        staff[1]=new Employee("Harry Hacker",50000,1989,10,1);
        staff[2]=new Employee("Tommy Tester",40000,1990,3,15);

        for(Employee e:staff)
            System.out.println("name" + e.getName()
                    +",salary=" + e.getSalary());
    }
}

class Employee
{
    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/100;
        salary+=raise;
    }
    private String name;
    private double salary;
    private Date hireDay;
}
class Manager extends Employee
{
    super(n,s,year,month,day);
    bonus=0;
}
public double getSalary()
{
    double baseSalary=super.getSalary();
    return baseSalary+bonus;
}
public void setBonus(double b)
{
    bonus=b;
}
private double bonus;
}

搭上奋斗的班车 2009-01-11 23:37 发表评论

特性论述：重载构造器、默认构造函数、对象初始化、静态初始化、实例域初始化

搭上奋斗的班车 — Wed, 07 Jan 2009 16:05:00 GMT

import java.util.*;
public class ConstructorTest
{
    public static void main(String[] args)
    {
        Employee[] staff=new Employee[3];

        staff[0]=new Employee("Harry",40000);
        staff[1]=new Employee(6000);
        staff[2]=new Employee();

        for(Employee e:staff)
            System.out.println("name=" + e.getName()
                    +",id=" + e.getId()
                    +",salary="+e.getSalary());
    }
}

class Employee
{
    public Employee(String n,double s)
    {
        name=n;
        salary=s;
    }
    public Employee(double s)
    {
        this("Employee #"+nextId,s);
    }
    public Employee()
    {
    }
    public String getName()
    {
        return name;
    }
    public double getSalary()
    {
        return salary;
    }
    public int getId()
    {
        return id;
    }
    private static int nextId;
    private int id;
    private String name="";
    private double salary;

    static
    {
        Random generator= new Random();
        nextId=generator.nextInt(10000);
    }
    {
        id=nextId;
        nextId++;
    }
}

搭上奋斗的班车 2009-01-08 00:05 发表评论

一个显示当前月的日历小程序

搭上奋斗的班车 — Tue, 06 Jan 2009 14:21:00 GMT

import java.util.*;
public class CalendarTest
{
    public static void main(String[] args)
    {
        GregorianCalendar d=new GregorianCalendar();

        int today=d.get(Calendar.DAY_OF_MONTH);
        int month=d.get(Calendar.MONTH);


        d.set(Calendar.DAY_OF_MONTH,1);

        int weekday=d.get(Calendar.DAY_OF_WEEK);

        System.out.println(" Sun  Mon  Tue  Wed  Thu  Fri  Sat");

        for(int i=Calendar.SUNDAY;i<weekday;i++)
            System.out.print("     ");

        do{
            int day=d.get(Calendar.DAY_OF_MONTH);
            if(day==today)
            {
                System.out.print("  [");
                System.out.printf("%d",day);
            }
            else
            {
            System.out.printf("%4d",day);
            }
            if(day==today)
            {
                System.out.print("]");
            }
            else
            {
                System.out.print(" ");
            }
            if(weekday==Calendar.SATURDAY)
                System.out.println();

            d.add(Calendar.DAY_OF_MONTH,1);
            weekday=d.get(Calendar.DAY_OF_WEEK);
          }
        while(d.get(Calendar.MONTH)==month);

        if(weekday!=Calendar.SUNDAY)
            System.out.println();
    }
}

搭上奋斗的班车 2009-01-06 22:21 发表评论

不规则数组的应用。

搭上奋斗的班车 — Tue, 30 Dec 2008 10:09:00 GMT

/*
程序的运行结果如下：

   1
   1   1
   1   2   1
   1   3   3   1
   1   4   6   4   1
   1   5  10  10   5   1
   1   6  15  20  15   6   1
   1   7  21  35  35  21   7   1
   1   8  28  56  70  56  28   8   1
   1   9  36  84 126 126  84  36   9   1
   1  10  45 120 210 252 210 120  45  10   1

*/

public class LotteryArray
{
public static void main(String[] args)
{
  final int NMAX=10;

  int[][] odds=new int[NMAX+1][];
  for(int n=0;n<=NMAX;n++)
   odds[n]=new int[n+1];

  for(int n=0;n<odds.length;n++)//行
   for(int k=0;k<odds[n].length;k++)
   {
    int lotteryOdds=1;
    for(int i=1;i<=k;i++)
     lotteryOdds=lotteryOdds*(n-i+1)/i;

    odds[n][k]=lotteryOdds;
   }
  for(int[] row:odds)
  {
   for(int odd:row)
    System.out.printf("%4d",odd);
   System.out.println();
  }
}
}

搭上奋斗的班车 2008-12-30 18:09 发表评论

很简单的选择和重复语句的帮助系统

搭上奋斗的班车 — Sat, 27 Dec 2008 15:32:00 GMT

public class Menu
{
    public static void main(String[] args)
    throws java.io.IOException
    {
        char choice;
        do{
            System.out.println("=====Help on=====");
            System.out.println(" 1. if");
            System.out.println(" 2. switch");
            System.out.println(" 3. while");
            System.out.println(" 4. do-while");
            System.out.println(" 5. for\n");
            System.out.println("Choose one between one  and five:");
            choice = (char) System.in.read();

        }while( choice < '1' || choice > '5');

    System.out.println("\n");

    switch(choice)
    {

        case '1':
        System.out.println("The if:\n");
        System.out.println("if(condition) statement;");
        System.out.println("else statement;");
        break;

        case '2':
        System.out.println("The switch:\n");
        System.out.println("switch(expression) {");
        System.out.println(" case constant:");
        System.out.println(" statement sequence");
        System.out.println(" break;");
        System.out.println(" // ");
        System.out.println("}");
        break;

        case '3':
        System.out.println("The while:\n");
        System.out.println("while(condition) statement;");
        break;

        case '4':
        System.out.println("The do-while:\n");
        System.out.println("do {");
        System.out.println(" statement;");
        System.out.println("} while (condition);");
        break;

        case '5':
        System.out.println("The for:\n");
        System.out.print("for(init; condition; iteration)");
        System.out.println(" statement;");
        break;

    }
    }
}

搭上奋斗的班车 2008-12-27 23:32 发表评论

java循环示例代码集锦--while循环（1）

搭上奋斗的班车 — Thu, 25 Dec 2008 16:22:00 GMT

class NoBody
{
    public static void main(String args[])
    {
        int i, j;
        i = 130;
        j = 200;

        while(++i < --j) ; // 找出两数的中间点。
        System.out.println("Midpoint is " + i);
    }
}

搭上奋斗的班车 2008-12-26 00:22 发表评论

java循环示例代码集锦--for循环 Four.

搭上奋斗的班车 — Thu, 25 Dec 2008 16:04:00 GMT

public class XingHaoFour
{
    public static void main(String[] args)
    {
        for(int i=10;i>0;i--)
        {
            for(int j=i;j>1;j--)
            {
                System.out.print("  ");
            }

            for(int n=i;n<11;n++)
            {
                System.out.print("*");
            }
        System.out.println("");
        }
    }
}

/*
此图是打印结果:

　　　　　　　　　*
　　　　　　　　**
　　　　　　　***
　　　　　　****
　　　　　*****
　　　　******
　　　*******
　　********
　*********
**********

*/

搭上奋斗的班车 2008-12-26 00:04 发表评论

java循环示例代码集锦--for循环 Three.

搭上奋斗的班车 — Thu, 25 Dec 2008 15:55:00 GMT

public class XingHaoThree
{
    public static void main(String[] args)
    {
        for(int i=10;i>0;i--)
        {
            for(int j=i;j>1;j--)
            {
                System.out.print("*");
            }
        System.out.println("");
        }
    }
}

/*
此图是运行结果:

**********
*********
********
*******
******
*****
****
***
**
*

*/

搭上奋斗的班车 2008-12-25 23:55 发表评论

java循环示例代码集锦--for循环 two.

搭上奋斗的班车 — Tue, 23 Dec 2008 15:32:00 GMT

public class XingHaoTwo
{
    public static void main(String[] args)
    {
        for(int i=10;i>0;i--)//控制输出行数
        {
            for(int s=i;s<11;s++)//控制星号输出
            {
                System.out.print("*");
            }
        System.out.print("\n");
        }

    }
}

搭上奋斗的班车 2008-12-23 23:32 发表评论

java循环示例代码集锦--for循环 one.

搭上奋斗的班车 — Tue, 23 Dec 2008 15:27:00 GMT

public class XingHaoOne
{
    public static void main(String[] args)
    {
        for(int i=10;i>0;i--)//控制输出行数
        {
            for(int s=0;s<10-i;s++)//控制空格输出
            {
                System.out.print(" ");
            }
            for(int x=i;x>0;x--)//控制星号输出
            {
                System.out.print("*");
            }
        System.out.print("\n");
        }

    }
}

搭上奋斗的班车 2008-12-23 23:27 发表评论

一个关于数组的

搭上奋斗的班车 — Sun, 05 Oct 2008 10:17:00 GMT

1-10 这十个数字要求分成若干组，每组七个数字。每组内部的数字不能重复，组与组之间的七个数字不能完全相同。

import java.util.Arrays;

public class Seven {

    /**
     * @author cqusnail
     */
    public static void main(String[] args) {

        Seven s = new Seven();


        int t = 0;
        int[] r;
        int[][] rr = new int[200][7];

        again:
        //理论上只能生成120组，当然为了检验，你也可以把 t 的上限设大一些
        while(t<120)
        {

            r = s.s_Sort();
            //比较新产生的数组与已经存在的数组中的元素是否相等
            for(int e =0;e<t+1;e++)
            {

                //比较新产生的数组与当前的数组是否相等

                    if(Arrays.equals(r, rr[e]))
                        continue again;

             }
            //如果产生的数组与已经存在的数组不相等，则放入rr数组，并打印

            {
                rr[t]=r;

                System.out.print(" 第 "+t+" 组    ");
                for(int p=0;p<7;p++)
                {
                    System.out.print(" "+r[p]+"  ");

                }
            }

             System.out.println();
             t++;

        }
    }
    //产生一组七个数字，每组内部的数字不能重复，并且排好序
    private int[] s_Sort()
    {
        int[] str = new int[7];
        int[] a = new int[10];
        int temp = 10;
        int temp2;

        for(int j=0;j<10;j++)
        {
            a[j]=j+1;
        }

        for(int i=0;i<7;i++)

        {

            temp2 = (int)(Math.random()*temp);
            str[i]= a[temp2];
            for(int k=temp2;k<temp-1;k++)
            {
                a[k]=a[k+1];
            }
            temp--;

        }

        Arrays.sort(str);

        return str;
    }

}

搭上奋斗的班车 2008-10-05 18:17 发表评论