第四章类、对象和接口

1、第四章 类、对象和接口例子1class XiyoujiRenwu float height,weight; String head, ear,hand,foot, mouth; void speak(String s) System.out.println(s); class A public static void main(String args) XiyoujiRenwu zhubajie; /声明对象 zhubajie=new XiyoujiRenwu(); /为对象分配内存，使用new 运算符和默认的构造方法 例子2class Point int x,y; Point(int a,i

2、nt b) x=a; y=b; public class A public static void main(String args) Point p1,p2; /声明对象p1和p2 p1=new Point(10,10); /为对象分配内存，使用 new 和类中的构造方法 p2=new Point(23,35); /为对象分配内存，使用 new 和类中的构造方法例子3class XiyoujiRenwu float height,weight; String head, ear,hand,foot,mouth;void speak(String s) head="歪着头"

3、 System.out.println(s); class Example4_3 public static void main(String args) XiyoujiRenwu zhubajie,sunwukong;/声明对象 zhubajie=new XiyoujiRenwu(); /为对象分配内存 sunwukong=new XiyoujiRenwu(); zhubajie.height=1.80f; /对象给自己的变量赋值 zhubajie.head="大头" zhubajie.ear="一双大耳朵" sunwukong.height=1.62

4、f; /对象给自己的变量赋值 sunwukong.weight=1000f; sunwukong.head="绣发飘飘" System.out.println("zhubajie的身高："+zhubajie.height); System.out.println("zhubajie的头："+zhubajie.head); System.out.println("sunwukong的重量："+sunwukong.weight); System.out.println("sunwukong的头："+

5、sunwukong.head); zhubajie.speak("俺老猪我想娶媳妇"); /对象调用方法 System.out.println("zhubajie现在的头："+zhubajie.head); sunwukong.speak("老孙我重1000斤，我想骗八戒背我"); /对象调用方法 System.out.println("sunwukong现在的头："+sunwukong.head); 例子4class 梯形 float 上底,下底,高,面积; 梯形(float x,float y,float h)

6、 上底=x; 下底=y; 高=h; float 计算面积() 面积=(上底+下底)*高/2.0f; return 面积; void 修改高(float height) 高=height; float 获取高() return 高; public class Example4_4 public static void main(String args) 梯形 laderOne=new 梯形(12.0f,3.5f,50),laderTwo=new 梯形(2.67f,3.0f,10); System.out.println("laderOne的高是:"+laderOne.获取高(

7、); System.out.println("laderTwo的高是:"+laderTwo.获取高(); System.out.println("laderOne的面积是:"+laderOne.计算面积(); System.out.println("laderTwo的面积是:"+laderTwo.计算面积(); laderOne.修改高(10); float h=laderOne.获取高(); laderTwo.修改高(h*2); System.out.println("laderOne现在的高是:"+laderO

8、ne.获取高(); System.out.println("laderTwo现在的高是:"+laderTwo.获取高(); System.out.println("laderOne现在的面积是:"+laderOne.计算面积(); System.out.println("laderTwo现在的面积是:"+laderTwo.计算面积(); 例子5class People String face; void setFace(String s) face=s; class A void f(int x,double y,People p)

9、x=x+1; y=y+1; p.setFace("笑脸"); System.out.println("参数x和y的值分别是:"+x+","+y); System.out.println("参数对象p的face是:"+p.face); public class Example4_5 public static void main(String args) int x=100; double y=100.88; People zhang=new People(); zhang.setFace("很严肃的样子&

10、quot;); A a=new A(); a.f(x,y,zhang); System.out.println("main方法中x和y的值仍然分别是:"+x+","+y); System.out.println("main方法中对象zhang的face是:"+zhang.face); 例子6class 圆 double 半径; 圆(double r) 半径=r; double 计算面积() return 3.14*半径*半径; void 修改半径(double 新半径) 半径=新半径; double 获取半径() return 半径;

11、 class 圆锥 圆 底圆; double 高; 圆锥(圆 circle,double h) this.底圆=circle; this.高=h; double 计算体积() double volume; volume=底圆.计算面积()*高/3.0; return volume; void 修改底圆半径(double r) 底圆.修改半径(r); double 获取底圆半径() return 底圆.获取半径(); class Example4_6 public static void main(String args) 圆 circle=new 圆(10); 圆锥 circular=new

12、圆锥(circle,20); System.out.println("圆锥底圆半径:"+circular.获取底圆半径(); System.out.println("圆锥的体积:"+circular.计算体积(); circular.修改底圆半径(100); System.out.println("圆锥底圆半径:"+circular.获取底圆半径(); System.out.println("圆锥的体积:"+circular.计算体积(); 例子7class 梯形 float 上底,高; static float

13、下底;梯形(float x,float y,float h) 上底=x; 下底=y; 高=h; float 获取下底() return 下底; void 修改下底(float b) 下底=b; class Example4_7 public static void main(String args) 梯形 laderOne=new 梯形(3.0f,10.0f,20),laderTwo=new 梯形(2.0f,3.0f,10); 梯形.下底=200; /通过类名操作类变量 System.out.println("laderOne的下底:"+laderOne.获取下底(); S

14、ystem.out.println("laderTwo的下底:"+laderTwo.获取下底(); laderTwo.修改下底(60); /通过对象操作类变量 System.out.println("laderOne的下底:"+laderOne.获取下底(); System.out.println("laderTwo的下底:"+laderTwo.获取下底(); 例子8class Fibi public static long fibinacii(int n) long c=0; if(n=1|n=2) c=1; else c=fibi

15、nacii(n-1)+fibinacii(n-2); return c; public class Example4_8 public static void main(String args) System.out.println(Fibi.fibinacii(7); 例子9package tom.jiafei;public class PrimNumber public void getPrimnumber(int n) int sum=0,i,j; for(i=1;i<=n;i+) for(j=2;j<=i/2;j+) if(i%j=0) break; if(j>i/2

16、) System.out.print(" "+i); public static void main(String args) PrimNumber p=new PrimNumber(); p.getPrimnumber(20); 例子10import java.applet.Applet;import java.awt.*;public class Example4_10 extends Applet Button redbutton; public void init() redbutton=new Button("我是一个红色的按钮"); redb

17、utton.setBackground(Color.red);redbutton.setForeground(Color.white); add(redbutton); 例子11import tom.jiafei.*; /引入包tom.jiafei中的类public class Example4_11 public static void main(String args) PrimNumber num=new PrimNumber();/用包tom.jiafei中的类创建对象 num.getPrimnumber(30); 例子12public class Example4_12 public

18、 static void main(String args) PrimNumber num=new PrimNumber();/要保证PrimNuber类和Example4_12类在同一目录中 num.getPrimnumber(120); Trangel.javapackage tom.jiafei;public class Trangle double sideA,sideB,sideC; boolean boo; public Trangle(double a,double b,double c) sideA=a; sideB=b; sideC=c; if(a+b>c&&a

19、mp;a+c>b&&c+b>a) System.out.println("我是一个三角形"); boo=true; else System.out.println("我不是一个三角形"); boo=false; public void 计算面积() if(boo) double p=(sideA+sideB+sideC)/2.0; double area=Math.sqrt(p*(p-sideA)*(p-sideB)*(p-sideC) ; System.out.println("面积是:"+area);

20、else System.out.println("不是一个三角形,不能计算面积"); public void 修改三边(double a,double b,double c) sideA=a; sideB=b; sideC=c; if(a+b>c&&a+c>b&&c+b>a) boo=true; else boo=false; 例子13import tom.jiafei.Trangle;class Example4_13 public static void main(String args) Trangle trangle

21、=new Trangle(12,3,1); trangle.计算面积(); trangle.修改三边(3,4,5); trangle.计算面积(); 例子14class Example4_14 private int money;Example4_14() money=2000; private int getMoney() return money; public static void main(String args) Example4_14 exa=new Example4_14();exa.money=3000;int m=exa.getMoney(); System.out.pri

22、ntln("money="+m); 例子15class Father private int money; float weight,height; String head; void speak(String s) System.out.println(s); class Son extends Father String hand,foot; public class Example4_15 public static void main(String args) Son boy; boy=new Son(); boy.weight=1.80f; boy.height=

23、120f; boy.head="一个头" boy.hand="两只手 " boy.foot="两只脚" boy.speak("我是儿子"); System.out.println(boy.hand+boy.foot+boy.head+boy.weight+boy.height); 例子16class Chengji float f(float x,float y) return x*y; class Xiangjia extends Chengji float f(float x,float y) return x

24、+y ; public class Example4_16 public static void main(String args) Xiangjia sum; sum=new Xiangjia(); float c=sum.f(4,6); System.out.println(c); 例子17class Area float f(float r ) return 3.14159f*r*r; float g(float x,float y) return x+y; class Circle extends Area float f(float r) return 3.14159f*2.0f*r

25、; public class Example4_17 public static void main(String args) Circle yuan; yuan=new Circle(); float length=yuan.f(5.0f); float sum=yuan.g(232.645f,418.567f); System.out.println(length); System.out.println(sum); 例子18class A final double PI=3.1415926; public double getArea(final double r) return PI*

26、r*r; public class Example4_18 public static void main(String args) A a=new A(); System.out.println("面积："+a.getArea(100); 例子19class 类人猿 private int n=100; void crySpeak(String s) System.out.println(s); class People extends 类人猿 void computer(int a,int b) int c=a*b; System.out.println(c); voi

27、d crySpeak(String s) System.out.println("*"+s+"*"); class Example4_19 public static void main(String args) 类人猿 monkey=new People(); monkey.crySpeak("I love this game");People people=(People)monkey; puter(10,10); 例子20class 动物 void cry() class 狗 extends 动物 void cry() Syst

28、em.out.println("汪汪."); class 猫 extends 动物 void cry() System.out.println("喵喵."); class Example4_20 public static void main(String args) 动物 dongwu; dongwu=new 狗(); dongwu.cry(); dongwu=new 猫(); dongwu.cry(); 例子21abstract class A abstract int min(int x,int y); int max(int x,int y) r

29、eturn x>y?x:y; class B extends A int min(int x,int y) return x<y?x:y; public class Example4_21 public static void main(String args) A a; B b=new B(); int max=b.max(12,34); int min=b.min(12,34); System.out.println("max="+max+" min="+min); a=b; max=a.max(12,34); System.out.pr

30、intln("max="+max); 例子22abstract class 图形 public abstract double 求面积();class 梯形 extends 图形 double a,b,h; 梯形(double a,double b,double h) this.a=a;this.b=b;this.h=h; public double 求面积() return(1/2.0)*(a+b)*h); class 圆形 extends 图形 double r; 圆形(double r) this.r=r; public double 求面积() return(3.1

31、4*r*r); class 堆 图形 底; double 高; 堆(图形 底,double 高) this.底=底; this.高=高; void 换底(图形 底) this.底=底; public double 求体积() return (底.求面积()*高)/3.0; public class Example4_22 public static void main(String args) 堆 zui; 图形 tuxing; tuxing=new 梯形(2.0,7.0,10.7); System.out.println("梯形的面积"+tuxing.求面积(); zui

32、=new 堆(tuxing,30); System.out.println("梯形底的堆的体积"+zui.求体积(); tuxing=new 圆形(10); System.out.println("半径是10的圆的面积"+tuxing.求面积(); zui.换底(tuxing); System.out.println("圆形底的堆的体积"+zui.求体积(); 例子23class Student int number;String name;Student() Student(int number,String name) this.

33、number=number;=name; System.out.println("I am "+name+ "my number is "+number); class Univer_Student extends Student boolean 婚否; Univer_Student(int number,String name,boolean b) super(number,name); 婚否=b; System.out.println("婚否="+婚否); public class Example4_23 pub

34、lic static void main(String args) Univer_Student zhang=new Univer_Student(9901,"和晓林",false); 例子24class Sum int n; float f() float sum=0; for(int i=1;i<=n;i+) sum=sum+i; return sum; class Average extends Sum int n; float f() float c; super.n=n; c=super.f(); return c/n; float g() float c;

35、 c=super.f(); return c/2; public class Example4_24 public static void main(String args) Average aver=new Average(); aver.n=100; float result_1=aver.f(); float result_2=aver.g(); System.out.println("result_1="+result_1); System.out.println("result_2="+result_2); 例子25interface Comp

36、utable int MAX=100; int f(int x);class China implements Computable int number; public int f(int x) /不要忘记public关键字 int sum=0; for(int i=1;i<=x;i+) sum=sum+i; return sum; class Japan implements Computable int number; public int f(int x) return 44+x; public class Example4_25 public static void main(

37、String args) China zhang; Japan henlu; zhang=new China(); henlu=new Japan(); zhang.number=991898+Computable.MAX; henlu.number=941448+Computable.MAX; System.out.println("number:"+zhang.number+"求和"+zhang.f(100); System.out.println("number:"+henlu.number+"求和"+hen

38、lu.f(100); 例子26interface 收费 public void 收取费用();interface 调节温度 public void controlTemperature();class 公共汽车 implements 收费 public void 收取费用() System.out.println("公共汽车:一元/张,不计算公里数"); class 出租车 implements 收费, 调节温度 public void 收取费用() System.out.println("出租车:1.60元/公里,起价3公里"); public voi

39、d controlTemperature() System.out.println("安装了Hair空调"); class 电影院 implements 收费,调节温度 public void 收取费用() System.out.println("电影院:门票,十元/张"); public void controlTemperature() System.out.println("安装了中央空调"); class Example4_26 public static void main(String args) 公共汽车 七路=new

40、公共汽车(); 出租车 天宇=new 出租车(); 电影院 红星=new 电影院(); 七路.收取费用(); 天宇.收取费用(); 红星.收取费用(); 天宇.controlTemperature(); 红星.controlTemperature(); 例子27interface ShowMessage void 显示商标(String s);class TV implements ShowMessage public void 显示商标(String s) System.out.println(s); class PC implements ShowMessage public void 显

41、示商标(String s) System.out.println(s); public class Example4_27 public static void main(String args) ShowMessage sm; sm=new TV(); sm.显示商标("长城牌电视机"); sm=new PC(); sm.显示商标("联想奔月5008PC机"); 例子28interface Computerable public double 求面积();class 梯形 implements Computerable double a,b,h;梯形(

42、double a,double b,double h) this.a=a;this.b=b;this.h=h; public double 求面积() return(1/2.0)*(a+b)*h); class 圆形 implements Computerable double r; 圆形(double r) this.r=r; public double 求面积() return(3.14*r*r); class 堆 Computerable 底; double 高; 堆(Computerable 底,double 高) this.底=底; this.高=高; void 换底(Compute

43、rable 底) this.底=底; public double 求体积() return (底.求面积()*高)/3.0; public class Example4_28 public static void main(String args) 堆 zui; Computerable bottom; bottom=new 梯形(2.0,7.0,10.7); System.out.println("梯形的面积"+bottom.求面积(); zui=new 堆(bottom,30); System.out.println("梯形底的堆的体积"+zui.求

44、体积(); bottom=new 圆形(10); System.out.println("半径是10的圆的面积"+bottom.求面积(); zui.换底(bottom); System.out.println("圆形底的堆的体积"+zui.求体积(); 例子29interface SpeakHello void speakHello();class Chinese implements SpeakHello public void speakHello() System.out.println("中国人习惯问候语：你好，吃饭了吗？ "

45、;); class English implements SpeakHello public void speakHello() System.out.println("英国人习惯问候语：你好，天气不错 "); class KindHello public void lookHello(SpeakHello hello) hello.speakHello(); public class Example4_29 public static void main(String args) KindHello kindHello=new KindHello(); kindHello

46、.lookHello(new Chinese(); kindHello.lookHello(new English(); 例子30class China final String nationalAnthem="义勇军进行曲" Beijing beijing; China() beijing=new Beijing(); String getSong() return nationalAnthem; class Beijing String name="北京" void speak() System.out.println("我们是"

47、+name+" 我们的国歌是:"+getSong(); public class Example4_30 public static void main(String args) China china=new China(); china.beijing.speak(); 例子31class Cubic double getCubic(int n) return 0; abstract class Sqrt public abstract double getSqrt(int x);class A void f(Cubic cubic) double result=cubic.getCubic(3); S