Java+2+程序设计实用教程.doc

Java+2+程序设计实用教程(2)例3-1 Fish类的定义class Fish /关键字class用来定义类Fish String name ; /描述Fish的名字 String theColor; /描述Fish的颜色 void setValue(String n,String c ) /设置值：名字，颜色name=n;theColor=c;void swimming( ) /Fish最大的特性是能游泳 System.out.println(i can swimming.);void output( ) System.out.println(my name is:+name+ i like:+theColor);public static void main(String args) Fish clownFish = new Fish(); /创建Fish的变量clownFish clownFish.setValue(nemo,red); /调用Fish中的方法（函数）为f赋值 clownFish.output( ); /输出f所描述的鱼的信息 clownFish.swimming( ); /Fish会游泳例3-2 定义一个学生类public class StudentClssDemoString name ,dept,sex;int age,english,maths,computer;void setData(String n,String s,String d,int a, int e,int m,int c) /成员方法 name=n; age=a; /类的成员变量在整个类内有效 sex=s; dept=d; english=e; maths=m; computer=c;int total() /成员方法 int sum= english+maths+computer; /sum是方法体中的局部变量 return sum; /局部变量sum有效范围是它所在语句块void print() /成员方法 System.out.println(姓名:+name+年龄:+age+性别:+sex+系别:+dept); System.out.println(英语:+english+数学:+maths+计算机:+computer); public static void main(String argv) StudentClssDemo s=new StudentClssDemo(); /创建对象 s.setData(张楠,男,计算机系,19,80,85,90); /调用成员方法 s.print(); /成员方法的调用 System.out.println(总分:+s.total(); /成员方法的调用例3-3 Book类的定义与对象的实例化class Book String name; float price; int width, height; Book(String n,float p,int w,int h) /构造方法，用于实例化对象 name=n; price=p; width =185; height =260; void output() System.out.println(name:+name+t+price:+price); public static void main(String args) Book b1; /声明对象 b1=new Book(Java2 Programming,31.0f,185,260); /实例化对象b1 Book b2=new Book(C+ Programming,31.0f,185,260); /声明并实例化对象b2 b1.output(); /通过对象b1调用方法output（） b2.output(); /通过对象b2调用方法output（） 例3-4 定义一个描述书的类class BookDemo String name; float price; void output() System.out.println(name:+name+t+price:+price); public static void main(String args) BookDemo b1; /声明对象 b1=new BookDemo(); /实例化对象，数据成员被初始化为空值 b1.output(); =java2 Programming; /通过对象名为成员变量赋值 b1.price=32.5f; /通过对象名为成员变量赋值 b1.output(); 例3-5 带构造方法的类class BookDemo1 String name; float price; BookDemo1(String n,float p) /构造方法，与类同名 name=n; price=p; void output() System.out.println(name:+name+t+price:+price); public static void main(String args) BookDemo1 b1; /声明对象 b1=new BookDemo1(Java2,32.5f); /自动调用构造方法实例化对象 b1.output(); 例3-6 带访问控制权限修饰符的类class Book String name; private float price; /私有成员 Book(String n,float p) name=n; price=p; public void setPrice(float p) /公有成员，类的外部接口 price=p; public void output() /公有成员，类的外部接口 System.out.println(name:+name+t+price:+price); public class useBookDemo public static void main(String args) Book b=new Book(Java2,52.5f); b.output(); /可以访问类Book的公有成员 b.price=32.0f; /非法访问，其他类不能访问类Book的私有成员 b.setPrice(32.0f); /正确的访问 b.output(); 例3-7 带静态成员变量的类class useBook String name; float price; int count=0; /记录创建对象的个数 static int bookNumber=100; /静态变量，书的起始编号为100 useBook(String n,float p) name=n; price=p; count+; /记录创建对象个数,增加1 bookNumber+; /书号实现自动增加1 void output() prt(name:+name+t+price:+price+t); prt(bookNumber:+bookNumber+t+count:+count+n); public static void prt(String s) System.out.print(s); public static void main(String args) useBook b1,b2,b3; /声明对象 b1=new useBook(Java2,36.0f); b1.output(); b2=new useBook(C+,40.0f); b2.output(); b3=new useBook(VB ,35.0f); b3.output(); 例3-8 静态变量的访问/*class Book String name; private float price; Book(String n,float p) name=n; price=p; public void setPrice(float p) /类的外部接口 price=p; public void output() /类的外部接口 System.out.println(name:+name+t+price:+price); public class useBook public static void main(String args) Book b=new Book(Java2,32.5f); /自动调用构造方法实例化对象 b.output(); b.price=100.0f; /非法访问 b.output(); */*class useBook String name; float price; int count=0; /记录创建对象的个数 static int bookNumber=100; /静态变量，书的起始编号为100 useBook(String n,float p) name=n; price=p; count+; /记录创建对象个数,增加1 bookNumber+; /书号实现自动增加1 void output() prt(name:+name+t+price:+price+t); prt(bookNumber:+bookNumber+t+count:+count+n); public static void prt(String s) System.out.print(s); public static void main(String args) useBook b1,b2,b3; /声明对象 b1=new useBook(Java2,36.0f); b1.output(); b2=new useBook(C+,40.0f); b2.output(); b3=new useBook(VB ,35.0f); b3.output(); */public class Circle static double PI=3.1415926; int radius; Circle(int r ) radius=r; double getArea( ) double area=radius*radius*PI;/创建对象后可以直接访问，也可以通过类名访问 return area; public static void main(String args) System.out.println(圆周率的值： +Circle.PI);/创建实例前，可访问 Circle c=new Circle(10); System.out.println(c.getArea(); 例3-9 带静态方法的类class Book String name; private float price; static int count; /静态变量，统计对象个数 Book(String n,float p) name=n; price=p; count+; /加1 public static void disCount() /静态方法 System.out.print(Count:+count+t); /只能访问静态成员 public void output() /实例方法 disCount(); /实例方法可以访问静态成员 System.out.println(name:+name+t+price:+price); public class useBookDemo2 public static void main(String args) Book.disCount(); /通过类名调用静态方法 System.out.print(n); /换行 Book b1=new Book(Java2,32.5f); b1.output(); Book b2=new Book(C+,32.5f); b2.output(); Book b3=new Book(Delphi,32.5f); b3.output(); Book.disCount(); /通过类名调用静态方法 例3-10 传值传递基本数据类型参数public class PassValue static void exchange(int a,int b) /静态方法才被main方法调用 int temp; temp=a; a=b; b=temp; public static void main(String args) int i=10; int j=100; System.out.println(before call:+i=+i+tj=+j); /调用前 exchange(i,j); System.out.println(after call:+i=+i+tj=+j); /调用后 例3-11 引用传递对象作为参数class Book String name; private float price; Book(String n, float p) /构造方法 name=n; price=p; static void change(Book a_book, String n, float p) /静态方法，对象作为参数 a_=n; a_book.price=p; public void output() /实例方法，输出对象信息 System.out.println(name:+name+t+price:+price); public class PassAddr public static void main(String args) Book b=new Book(Java2,32.5f); System.out.print(before call:t); /调用前 b.output(); b.change(b,C+,45.5f); /引用传递，对象b作为参数 System.out.print(after call:t); /调用后 b.output(); 例4-1 Object类常用方法class Book_Obj String name; private int price; Book_Obj(String n,int p) name=n; price=p; public static void prt(String s) System.out.println(s); public static void main(String args) String s1=new String(123456); String s2=new String(123456); prt(s2 equals s1:t+s2.equals(s1); /字符串对象s1和s2含有一样的信息 Book_Obj b1=new Book_Obj(Java2,40); Book_Obj b2=new Book_Obj(Java2,40); Book_Obj b=b1; /为对象b赋值 prt(b2.equals b1:t+b2.equals(b1); /不是一个对象实体返回false prt(b.equals b1:t+b.equals(b1); /指向同一个对象实体返回true prt(hashCode of b1:t+b1.hashCode(); prt(hashCode of b2:t+b2.hashCode(); prt(call toString() by b1:t+b1.toString(); prt(b2 auto call toString():t+b2); prt(Get the class name of b1:t+b1.getClass( ).getName(); 例4-2 子类继承超类成员class Animal String name; /默认成员变量 int age;protected int weight; /保护成员变量 图 4 2 Fish的运行结果 protected void setData(String n,int a,int w) /保护成员方法 name = n; age = a; weight=w; public void ShowInfo() System.out.println(name +t+ age +t+ weight); public class FishInherit extends Animal int SwimSpeed; public static void main(String args) Animal a = new Animal() ; a.setData(Shred,26,90); a.ShowInfo(); FishInherit f = new FishInherit(); f.setData(Nemo,1,6); /子类对象调用继承的方法初始化对象 f.SwimSpeed=76; /为新添加的成员变量赋值 f.ShowInfo( ); /子类对象调用继承的方法输出信息 例4-3 成员方法的重载public class ex_add public static int add(int x,int y) int sum =x+y; return sum; public static int add(int x,int y,int z) int sum =x+y+z; return sum; public static void main(String args) int i=10,j=20,k=30; System.out.println(i=+i+tj=+j+ +ti+j=+add(i,j); System.out.println(i=+i+tj=+j+tk=+k+ti+j+k=+add(i,j,k); 例4-4 构造方法的重载public class Book_cons static int no=1000; /图书编号,类成员变量 String name; private float price; Book_cons(String name, float price) =name; /this引用指名成员变量 this.price=price; no+; Book_cons(String name) /构造方法重载 this(name,0.0f); /调用同类的构造函数 Book_cons(float price) /构造方法重载 this(不知书名,price); Book_cons() /构造方法重载 this(不知书名,0.0f); public void output() /实例方法 System.out.print(书号t+no); System.out.println(t书名: +name+t价格: +price); public void output(String p) /成员方法重载 System.out.print(书号t+no); System.out.println(t书名: +name+t价格: +p); public static void main(String args) String p=不知价格; Book_cons b1=new Book_cons(Java2,32.5f); b1.output(); Book_cons b2=new Book_cons(C+); b2.output(p); Book_cons b3=new Book_cons(45.6f); b3.output(); Book_cons b4=new Book_cons(); b4.output(p); 例4-5 方法的覆盖class Animal protected String name; protected int age; public Animal(String n,int a) = n; this.age = a; public void ShowInfo() System.out.print(n+this.getClass().getName()+t); System.out.print(name +t+ age +t); public class FishDemo extends Animal int SwimSpeed; FishDemo(String n,int a,int s) super(n, a); /调用超类的构造方法 SwimSpeed=s; public void ShowInfo() /方法覆盖，增加新的功能 super.ShowInfo(); /调用超类的实例方法 System.out.println(SwimSpeed ); public static void main(String args) Animal a=new Animal(Shred,26); a.ShowInfo(); FishDemo f=new FishDemo(Nemo,1,6); f.SwimSpeed=76; f.ShowInfo(); 例4-6 超类可以引用子类对象class Animal protected String name; public Animal(String n) name = n; public void ShowInfo() System.out.print(the animalt); System.out.print(name +t); public void cry() System.out.print(Crying.n); class Fish extends Animal int SwimSpeed; Fish(String n, int s) super(n); /调用超类的构造方法 SwimSpeed=s; public void ShowInfo( ) /方法覆盖 System.out.print(the Fisht+name +t); System.out.print(Swimming speed:t+ SwimSpeed); public void cry() /方法覆盖 System.out.print(tBubbing.n); class Bird extends Animal int FlySpeed; Bird(String n,int f) super(n); /调用超类的构造方法 FlySpeed=f; public void ShowInfo( ) /方法覆盖 System.out.print(the Birdt+name +t); System.out.print(Flying speed:t+ FlySpeed); public void cry() /方法覆盖 System.out.print(tSinging.n); public class InheritDemo4_6 public static void main(String args) Animal a; a=new Animal(only a Animal); /超类对象引用子类创建的对象 a.ShowInfo(); /调用的是子类的覆盖后的方法 a.cry(); /调用的是子类的覆盖后的方法 a=(Animal)new Fish(Nemo ,20); a.ShowInfo(); a.cry(); Bird b=new Bird(Eagle ,80); a=b; /把一个子类对象直接赋值给超类对象 a.ShowInfo(); a.cry(); 例4-7 子类构造函数的定义class Animal /超类没显式定义构造函数 protected String name; public void setData(String n) name = n; public void ShowInfo() System.out.print(the animalt); System.out.print(name +t); public void cry() System.out.print(Crying.n); class Fish extends Animal int SwimSpeed; Fish(int s) /隐式调用超类的默认构造函数，将name设置为默认值null SwimSpeed=s; Fish(String n,int s) name=n; SwimSpeed=s; public void ShowInfo( ) /方法覆盖 System.out.print(the Fisht+name +t); System.out.print(Swimming speed:t+ SwimSpeed); public void cry() System.out.print(tBubbing.n); public class InheritDemo4_7 public static void main(String args) Fish a=new Fish(Nemo,60); a.ShowInfo(); a.cry(); Fish b=new Fish(60); /继承的成员name被设置为null b.ShowInfo(); b.cry(); 例4-8 抽象类的应用abstract class Animal /抽象类 protected String name; public abstract void move(); /没有方法体的抽象方法 public abstract void cry(); /没有方法体的抽象方法 public void ShowInfo(String n) System.out.print(n+n+t); System.out.print(name +t); class Fish extends Animal int SwimSpeed; Fish(String n,int s) name=n; SwimSpeed=s; public void move() /子类必须覆盖抽象类的抽象方法，鱼的走是游泳 System.out.print( swimming speed:t +SwimSpeed ); public void cry() /子类必须覆盖抽象类的抽象方法 System.out.print(tsinging.t ); class Bird extends Animal int FlySpeed; Bird(String n,int f) name=n; FlySpeed=f; public void move() /子类必须覆盖抽象类的抽象方法，鸟的走是飞翔 System.out.print( Flying speed:t +FlySpeed); public void cry() /子类必须覆盖抽象类的抽象方法 System.out.print(tbubbing.t ); class Snake extends Animal int CrawlSpeed; Snake(String n,int c) name=n; CrawlSpeed=c; public void move() /子类必须覆盖抽象类的抽象方法，蛇的走是爬行 System.out.print( Crawling speed:t +CrawlSpeed); public void cry() /子类必须覆盖抽象类的抽象方法 System.out.print(tchichi.t ); public class Animal_abstract public static void main(String args) Fish f=new Fish(Shark,80); f.ShowInfo(Fish); f.move(); f.cry(); Bird b=new Bird(Eagle,160); b.ShowInfo(Bird); b.move(); b.cry(); Snake s=new Snake(Nemo,20); s.ShowInfo(Cobra); s.move(); s.cry(); 例5-1 接口的实现interface theShape double PI=3.14159; double getArea();interface showShape void showInfor();public class Circle_inter implements theShape,showShape int r; Circle_inter(int r) this.r=r; public double getArea() /必须声明为public return r*r*PI; public void showInfor() /必须声明为public System.out.print(r= +r+tthe area: +getArea(); public static void main(String args) Circle_inter c=new Circle_inter(10); c. showInfor(); 例5-2 接口的应用interface access /接口的定义 void push(char e); char pop();class aStack implements access /一个堆栈类 private char element=new char50; private int top=0; public void push(char e) /实现接口的方法，压栈操作 elementtop+=e; public char pop() /实现接口的方法，出栈操作 return element-top; class aQueue implements access /一个队列类 private char element=new char50; private int front=0; private int rear=0; public void push(char e) /实现接口的方法，入队操作 elementrear+=e; public char pop() /实现接口的方法，出队操作 return elementfront+; public class useInterfaceDemo public static void showElement(char e) /输出一个字符 System.out.print(t+e); public static void main(String args) aStack s=new aStack(); s.push(A); s.push(B); s.push(1); s.push(2); System.out.println(The operation of Stack:); showElement(s.pop(); showElement(s.pop(); showElement(s.pop(); showElement(s.pop(); System.out.println(); aQueue q=new aQueue(); q.push(A); q.push(B); q.push(1); q.push(2); System.out.println(The operation of Queue:); showElement(q.pop(); showElement(q.pop(); showElement(q.pop(); showElement(q.pop(); 例5-3 内部类的定义public class InterclassDemo /外部类 class GetYear /内部类 private int i = 2008; pu