1. Multithreading
Threads and processes each have pros and cons and what difference it?
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The process is the smallest unit of resource allocation, the thread is the smallest unit of program execution.
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Process has its own separate address space, each started a process, the system will allocate address space for it, set up a data table to maintain the code segment, stack and data segments, this operation is very expensive. The thread is a shared process data, using the same address space, so the CPU changes than the process takes a much smaller thread, while creating a thread overhead is much smaller than the process.
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More convenient communication between threads, the thread in the same process share global variables, static variables and other data, and communication between processes carried out in a manner (IPC) communication. But how to handle the synchronization and mutual exclusion is the difficulty of writing multithreaded programs.
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But the program more robust multi-process, multi-threaded program as long as there is a thread dies, the whole process is dead, too, and a process dies the other will not have impact on the process, because the process has its own separate address space.
Thread multi-threaded :
By enabling multiple threads must use the thread in the start function.
runnable multi-threaded (avoid the limitations of single inheritance) :
runable is the interface, you can achieve multiple inheritance, but did not start method, so I can not just start a thread, but the thread constructor can be runnable as a parameter, so it can be passed via the constructor.
Mythread which implements runnable interface. After the multi-thread priority runnable.
The relationship between the thread and Runnable :
View source code:
We found runnable thread class implements an interface, inherited when the thread class before actually overwritten or runnable in the run method. And after performing start actually calls the run method, a map showing the relationship between the runnable and thread:
The thread started making calls when multithreading is the start method, and then find that the run method.
当通过thread类的构造方法传递了一个runnable的接口对象的时候，那么该接口对象将被thread类中的target属性所保存。在thread中调用start方法时会调用下面的run方法：
而这个覆写的run方法会调用runnable接口子类（上面图中的new Mythread对象，这个对象实现了runnable接口）被覆写过的run方法。
当有多个线程时的结构：
在实际情况下这里的线程对象就可能是各个用户。
模拟多个用户买票的程序：
内存如下图所示：
