初识Java面向对象

          最近在学Java，本来C++中的面向对象技术就没掌握的很好，于是非常认真的准备学，想补补OO。想下面是我近期的基于类与对象的小程序。在此罗列出来，供交流学习，望各位指正。

       在Java中创建对象都得用关键字new,然后调用构造函数。Java中的“=”连接对象是申明前者是后者的引用，即共用地址（实质是同一对象的不同名称而已）。

    

class Date {
int day, month, year;
Date(int D, int M, int Y) {
day = D;
month = M;
year = Y;
}
void Copy(Date date) {
this.day = date.day;
this.day = date.month;
this.day = date.year;
}
}

class Product {
Date When;
String Name;
double Price;
Product(Date date, String name, double price) {
this.When = date;//引用
this.Name = name;
this.Price = price;
}
}

public class Object1 {
static Product[] ArrayProduct= new Product[10];
static boolean IsInList(String TmpName) {
for (int i = 0; i < ArrayProduct.length; i++) {
if (0 == TmpName.compareTo(ArrayProduct[i].Name))
return true;
}
return false;
}

static int GetNumEterval(double low, double high) {
int count = 0;
for (int i = 0; i < ArrayProduct.length; i++) {
if (ArrayProduct[i].Price >= low && ArrayProduct[i].Price <= high)
count++;
}
return count;
}

public static void main(String[] str) {
String[] Name = new String[10];
Name[0] = "Apple";
Name[1] = "Pear";
Name[2] = "Banana";
Name[3] = "oringe";
Name[4] = "Rice";
Name[5] = "Noddle";
Name[6] = "Basketball";
Name[7] = "football";
Name[8] = "vollyball";
Name[9] = "tennis";
for (int i = 0; i < 10; i++) {
Date tmp = new Date((int) (31 * Math.random() % 32),
(int) (31 * Math.random() % 32), (int) (10 * Math.random()));
ArrayProduct[i] = new Product(tmp, Name[i], 10 * Math.random());
}
if (IsInList("Basketball")) {
System.out.println("Basketball is in the set!");
} else
System.out.println("Basketball is not in the set!");
System.out.println("The number of price between 3.0 and 7,0 is "
+ GetNumEterval(3, 7));
}
}

 

     下面将介绍Java中的静态成员（静态成员函数+静态成员变量）。在类定义时，使用关键字static可将成员定义为静态成员。特征是不管这个类创建了多少个对象，其静态成员只有一个副本，这个副本被所有的对象共享。静态数据成员必须进行初始化。在程序一开始运行时静态数据成员就必须存在，因为在程序运行中要调用，所以静态数据成员不能在任何函数内分配空间和初始化。最好在类的实现部分中完成静态数据成员的初始化。两种访问：类名.静态成员；对象名 . 静态成员。

class List {
String container;
List next;

List(String ele, List tail) {
container = ele;
next = tail;
}

// 判断ele是否属于list
static boolean BelongTo(String ele, List list) {
while (list != null) {
if (list.container == ele)
return true;
list = list.next;
}
return false;
}

// 顺序显示链表中的内容
static void Display(List list) {
while (list != null) {
System.out.print(list.container + "  ");
list = list.next;
}
System.out.println();
}

// 获取链表的长度
static int GetLength(List list) {
int ret = 0;
while (list != null) {
ret++;
list = list.next;
}
return ret;
}

// 插入元素
static List Insert(String ele, List list) {
return new List(ele, list);
}

// 删除某结点
static List Delete(String ele, List list) {
if (list == null)
return null;
if (list.container == ele)
return list.next;
List cur, pre;
pre = list;
cur = list.next;
while (cur != null && cur.container != ele) {
pre = cur;
cur = cur.next;
}
if (cur != null)
pre.next = cur.next;
return list;
}

// 复制产生新链表，此处倒置了
static List CopyAllListREV(List old) {
List New = null;
while (old != null) {
New = new List(old.container, New);
old = old.next;
}
return New;
}

// 复制产生新链表，此处未倒置了
static List CopyAllList(List old) {
if(old == null)
return old;
return new List(old.container, CopyAllList(old.next));
}
}

public class JavaList {

public static void main(String[] str) {

List MyList = new List("徐进", null);
MyList = new List("潘传军", MyList);
MyList = new List("叶温情", MyList);

System.out.println("下面是原链表的内容:");
List.Display(MyList);
System.out.println("综上链表的长度是" + List.GetLength(MyList));
System.out.println();

MyList = List.Insert("张伦干", MyList);
System.out.println("下面是插入后链表的内容:");
List.Display(MyList);
System.out.println("综上链表的长度是" + List.GetLength(MyList));
System.out.println();

MyList = List.Delete("张伦干", MyList);
System.out.println("下面是删除后链表的内容:");
List.Display(MyList);
System.out.println("综上链表的长度是" + List.GetLength(MyList));
System.out.println();

MyList=MyList.Insert("张伦干", MyList);
System.out.println("下面是插入后链表的内容:");
List.Display(MyList);
System.out.println("综上链表的长度是" + List.GetLength(MyList));
System.out.println();

List NewListREV = List.CopyAllListREV(MyList);
System.out.println("下面是复制后新链表的内容(倒置):");
List.Display(NewListREV);
System.out.println("综上链表的长度是" + List.GetLength(NewListREV));
System.out.println();

List NewList = List.CopyAllList(MyList);
System.out.println("下面是复制后新链表的内容(未倒置):");
List.Display(NewList);
System.out.println("综上链表的长度是" + List.GetLength(NewList));
System.out.println();
}
}

 

 

        一下是链表的排序算法。注意与C/C++中用指针或带头结点的链表的区别。函数sortRec(List2 list）采用的是二路归并的思想。

 

class List2 {
int container;
List2 next;

// 构造函数
List2(int ele, List2 tail) {
container = ele;
next = tail;
}

// 插入元素
List2 Insert(int ele) {
return new List2(ele, this);
}

//获取链表的长度
int Length(List2 list)
{
int len=0;
while(list!=null)
{
len++;
list=list.next;
}
return len;
}

//显示链表
void Display() {
List2 cur = this;
while (cur != null) {
System.out.print(cur.container + "---->");
cur = cur.next;
}
System.out.println("null");
}

//递归合并有序链表
static List2 Merge1(List2 u, List2 v) {
if (v == null)
return u;
if (u == null)
return v;
if (u.container < v.container) {
u.next = Merge1(u.next, v);
return u;
} else {
v.next = Merge1(v.next, u);
return v;
}
}

//非递归合并有序链表
static List2 Merge2(List2 u, List2 v) {
List2 tmp, New = null;
while (u != null && v != null) {
if (u.container <v.container) {
tmp = u.next;
u.next = New;
New = u;
u = tmp;
} else {
tmp = v.next;
v.next = New;
New = v;
v = tmp;
}
}
while (v!=null) {
tmp = v.next;
v.next = New;
New = v;
v = tmp;
}

while (u!=null) {
tmp = u.next;
u.next = New;
New = u;
u = tmp;
}
return New;
}

//链表的归并排序
static List2 sortRec(List2 list)
{
int len=list.Length(list);
if(len<=1)return list;
List2 pre,cur;
pre=list;
cur=list;
int i=0,tmp=len/2;
while(i<tmp)
{
i++;
pre=cur;
cur=cur.next;
}
pre.next=null;
return Merge1(sortRec(list), sortRec(cur));
}
}

public class JavaList2 {

public static void main(String[] str) {
List2 u = new List2(8, null);
u = u.Insert(6);
u = u.Insert(3);
u.Display();

List2 v = new List2(9, null);
v = v.Insert(7);
v = v.Insert(5);
v = v.Insert(4);
v = v.Insert(2);
v.Display();

List2 uv = u.Merge1(u, v);// uv=v.Merge(u,v);,uv=uv.Merge(u,v);uv=List2							// // .Merge(u,v);
uv.Display();

//List2 uv = u.Merge2(u, v);// uv=v.Merge(u,v);,uv=uv.Merge(u,v);uv=List2 //// .Merge(u,v);
//	uv.Display();

uv=uv.sortRec(uv);
uv.Display();
}
}

 

 

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