Java Multi-Threading programming

1. Threads:

A. Origin: Single task os--multi-tasking OS

B. Process: Each process corresponds to an application that allocates independent memory space

C. Thread: A thread is a separate execution branch within a process

D. Features: Shared content address space, lower switching costs

2. Thread creation and startup

A. Method one: (Thread)

① inherits the thread class, overriding the Run method--run method is only responsible for determining what this thread is going to do

 Public class extends thread{    publicvoid  run () {            }}

② Open Thread, call the Start method-the method allocates resources for the thread and then automatically calls This.run ()

New MyThread (); Mt.start ();         // Open Thread

③ if the Run method is called-no error, but only normal method call, no new thread is opened

B. Method two: (Runnable)

① implements the Runnable interface, overriding the Run method--run method is only responsible for determining what this thread is going to do

 Public class Implements runnable{    publicvoid  run () {    }}

② creates a thread object that passes in the implementation class object of the Runnable interface

Call Start () of the Thread object

Newnew  Thread (YT); Th.start ();

3. Thread Status

A. Process: ① new State (new Thread () object)--ready state (call Start (), but start () before calling run ()--run State (Start (), call Run ())--Death State (Run () method ends, resource recycling cleanup)

② Interrupt state: In the running state, the thread is not getting CPU execution for various reasons

B. Five reasons for interrupt status:

① Thread Priority: Thread priority of 10 levels, up to 10, minimum 1

A higher priority is only a greater chance of being executed, and it does not mean that a low priority

Th.setpriority (th.setpriority) (thread.max_priority) ;

② blocking: Causes the thread to break due to input/output (for example: Scanner)

③ sleep: The Sleep method of thread

Th.sleep (+);        // number of milliseconds to sleep

④ wait and wake: The Wait () and notify () method for Object

⑤ Hang: The Yield () method of Thread

4. Sync Lock

A. Keyword: synchronized

B. Meaning: When multiple threads access the same resource, it is possible that the resource data is confusing.

To ensure that the resource can only be used by one thread at a time, and then handed over to the next thread after use, we use synchronous technology.

C. The implementation of synchronization:

① Synchronization method: Add sync keyword on resource synchronized

 Public synchronized void Show (String name) {}

② Sync block: Use synchronized on the thread that invokes the resource

synchronized (this. rs) {        the. Rs.show (this. GetName ());} 

　　

Java Multi-Threading programming