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如果是通过定位new运算符创建的对象 在释放内存的时候不会调用对象的析构函数

char * buffer = new char[BUF];pc1 = new (buffer) JustTesting;delete [] buffer;// 这时候是不会调用~JustTesting()的

使用定位new运算符时 要手动的空值内存位置 不然一不小心就把之前见的对象覆盖掉了

pc3 = new (buffer + sizeof(JustTesting))  JustTesting("Better Idea", 6);

正常情况下 使用定位new 运算符时  delete [] 会有释放掉内存 但是如果依然希望程序能够调用析构函数的话

就显式的调用

pc1->~JustTesting();

我这里测试出来一个事情：

当调用析构函数后（定位new） 指针依然能够使用 当执行delete [] 释放数组之后才会出现数据异常的情况

如果是正常的new出来的对象 调用析构函数之后 对象指针就没用了

构造函数初始化对象const常量类型的成员时不能直接赋值。 因为人家是常量。需要在程序执行到构造函数体之前进行赋值：

Queue::Queue(int qs) : qsize(qs){    front = rear = NULL;    items = 0;}

这种用法仅限于构造函数。 :号后面的成员数量可以不止一个，const和声明为引用的类成员必须用这个方法赋值。

最后那个队列模式

其实就是单链表

// queue.h#ifndef QUEUE_H_#define QUEUE_H_class Customer{  private:    long arrive;    int processtime;  public:    Customer() {arrive = processtime = 0;}    void set(long when);    long when() const {return arrive;}    int ptime() const {return processtime;}};typedef Customer Item;class Queue{  private:    struct Node {Item item; struct Node * next;};    enum {Q_SIZE = 10};    Node * front;    Node * rear;    int items;    const int qsize;    Queue(const Queue & q) : qsize(0) {}    Queue & operator=(const Queue & q) {return *this;}  public:    Queue(int qs = Q_SIZE);    ~Queue();    bool isempty() const;    bool isfull() const;    int queuecount () const;    bool enqueue(const Item &item);    bool dequeue(Item &item);};#endif

// queue.cpp#include "queue.h"#include 
   
    Queue::Queue(int qs) : qsize(qs){  front = rear = NULL;  items = 0; }Queue::~Queue(){  Node * temp;  while (front != NULL)  {    temp = front;    front = front->next;    delete temp;  }}bool Queue::isempty() const{  return items == 0;}bool Queue::isfull() const{  return items == qsize;}int Queue::queuecount() const{  return items;}bool Queue::enqueue(const Item & item){  if (isfull())    return false;  Node * add = new Node;  add -> item = item;  add->next = NULL;  items++;  if (front == NULL)    front = add;  else    rear -> next = add;  rear = add;  return true;}bool Queue::dequeue(Item & item){  if (front == NULL)    return false;  item = front -> item;  items--;  Node * temp = front;  front = front -> next;  delete temp;  if (items == 0)    rear = NULL;  return true;}void Customer::set(long when){  processtime = std::rand() % 3 + 1;  arrive = when;}
   

bank.cpp#include 
   
    #include 
    
     #include 
     
      #include "queue.h"const int MIN_PER_HR = 60;bool newcustomer(double x);int main(){  using std::cin;  using std::cout;  using std::endl;  using std::ios_base;  std::srand(std::time(0));  cout << "Case Study: Bank of Heather Automatic Teller\n";  cout << "Enter maximum size of queue: ";  int qs;  cin >> qs;  Queue line(qs);  cout << "Enter the number of simulation hours: ";  int hours;  cin >> hours;  long cyclelimit = MIN_PER_HR * hours;  cout << "Enter the average number of customers per hour: ";  double perhour;  cin >> perhour;  double min_per_cust;  min_per_cust = MIN_PER_HR / perhour;  Item temp;  long turnaways = 0;  long customers = 0;  long served = 0;  long sum_line = 0;  int wait_time = 0;  long line_wait = 0;  for (int cycle = 0; cycle < cyclelimit; cycle++)  {    if (newcustomer(min_per_cust))    {      if (line.isfull())        turnaways++;      else      {        customers++;        temp.set(cycle);        temp.set(cycle);        line.enqueue(temp);      }    }    if (wait_time <= 0 && !line.isempty())    {      line.dequeue(temp);      wait_time = temp.ptime();      line_wait += cycle - temp.when();      served++;    }    if (wait_time > 0)      wait_time--;    sum_line += line.queuecount();  }  if (customers > 0)  {    cout << "customers accepted: " << customers <
     
    
   

总结：

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