实训JAVA语言设计——类设计训练

最新推荐文章于 2024-01-23 11:48:46 发布

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#java #语言 #存储

本文通过三个实例介绍如何使用Java进行图形界面编程：绘制矩形、显示学生信息及使用构造方法和静态成员变量。

1.三角形类:

import java.awt.*;

import java.applet.*;

class rectangles //定义 rectangles类

{

public int Width;

public int Height;

public rectangles(int CWidth, int CHeight) //构造方法

{

Width=CWidth;

Height=CHeight;

}//构造方法定义毕

public void Showrectangle(Graphics g,int x,int y)

{

g.drawString("Width:"+Width,x,y);

g.drawString("Height:"+Height,x,y+20);

g.drawString("Area:"+Height*Width,x,y+40);

}

} // dogs类定义毕

public class c4_1 extends Applet

{

public void paint(Graphics g)

{

rectangles myrect=new rectangles(20,30);

myrect.Showrectangle(g,25,120);

}

//html文件:

<html><head><title>applet program</title></head><body><applet code="a.class"

Width=200 height=250></applet></body></html>

2.学生信息

import java.awt.*;

import java.applet. *;

class students //定义students类

{

//以下三行定义students类的数据成员

public String stu_NO ;

public String stu_name;

public int grade1;

public int grade2;

//以下六行是students类的成员方法Showstudent( )的定义

public void Showstudent(Graphics g,int x,int y)

{

g.drawString("stu_N.O:"+stu_NO,x,y);

g.drawString("stu_name:"+stu_name,x,y+20);

g.drawString("totalgrade:"+(grade1+grade2),x,y+40);

}

//成员方法Showstudent( )定义完成

}// students类定义毕

public class c4_2 extends Applet

{

public void paint(Graphics g)

{

//以下为创建对象

students liuxing; //声明了一个名为liuxing的对象，它属于students类

liuxing=new students( ); //建立lixing对象，为它分配存储空间

students hanfeng=new students( );//声明hanfeng对象的同时建立该对象

students yingwei=new students( );//声明yingwei对象的同时建立该对象

students zhaoke=new students( );//声明zhaoke对象的同时建立该对象

students lishu=new students( );//声明lishu对象的同时建立该对象

//以下几行引用对象的数据成员，将一组值赋给对象的数据成员

liuxing.stu_name="liuxing";

liuxing.stu_NO="10010";

liuxing.grade1=95;

liuxing.grade2=94;

hanfeng.stu_name="hanfeng";

hanfeng.stu_NO="10011";

hanfeng.grade1=85;

hanfeng.grade2=92;

yingwei.stu_name="yingwei";

yingwei.stu_NO="10012";

yingwei.grade1=68;

yingwei.grade2=84;

zhaoke.stu_name="zhaoke";

zhaoke.stu_NO="10013";

zhaoke.grade1=75;

zhaoke.grade2=77;

lishu.stu_name="lishu";

lishu.stu_NO="10014";

lishu.grade1=89;

lishu.grade2=91;

//以下两行引用对象的成员方法

liuxing.Showstudent(g,25,25);

hanfeng.Showstudent(g,200,25);

yingwei.Showstudent(g,25,120);

zhaoke.Showstudent(g,200,120);

lishu.Showstudent(g,25,240); } }

3.用构造方法写:

import java.awt.*;

import java.applet.*;

class students //定义 students类

{

public String stu_NO ;

public String stu_name;

public int grade1;

public int grade2;

public students(String Cstu_NO,String Cstu_name,int Cgrade1,int Cgrade2) //构造方法

{

stu_NO=Cstu_NO;

stu_name=Cstu_name;

grade1=Cgrade1;

grade2=Cgrade2;

}//构造方法定义毕

public void Showstudent(Graphics g,int x,int y)

{

g.drawString("stu_NO:"+stu_NO,x,y);

g.drawString("stu_name:"+stu_name,x,y+20);

g.drawString("totalgrade:"+(grade1+grade2),x,y+40);

}

} // dogs类定义毕

public class c4_3 extends Applet

{

public void paint(Graphics g)

{

students liuxing=new students("10010","liuxing",95,94);

students hanfeng=new students("10011","handeng",85,92);

students yingwei=new students("10012","yingwei",68,84);

students zhaoke=new students("10013","zhaoke",75,77);

students lishu=new students("10014","lishu",89,91);

liuxing.Showstudent(g,25,25);

hanfeng.Showstudent(g,200,25);

yingwei.Showstudent(g,25,120);

zhaoke.Showstudent(g,200,120);

lishu.Showstudent(g,25,240);

}

4. 用pulic类来定义一个无修饰符的static,final类!

import java.awt.*;

import java.applet.*;

class pp{

static int n=33;

final int nn; //声明nn,但没有赋初值

final int k=55; //声明k并赋初值40

pp( )

{ nn= ++n; }//在构造方法中给nn赋值

}

public class c4_4 extends Applet

{

public void paint(Graphics g)

{

pp m1=new pp( ); //创建对象m1，使其静态数据成员nn的值为21

pp m2=new pp( ); //创建对象m2，使其静态数据成员nn的值为22

// m1.nn=90; //这是一个错误的赋值语句，因为nn是标识符常量

g.drawString("m2.nn="+m2.nn,20,30);

g.drawString("m2.k="+m2.k,20,50);

g.drawString("m1.nn="+m1.nn,20,70);

g.drawString("m1.k="+m1.k,20,90);

g.drawString("m1.nn="+m1.nn,20,110);g.drawString("m2.k="+m2.k,20,130);