Example Analysis of Java Thread Safety and synchronization
This article introduces the relevant knowledge of "Java thread safety and synchronization case analysis". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!
Thread safety issues
Multiple threads may share (access) the same resource
For example, accessing the same object, the same variable, the same file
When multiple threads access the same resource, it is easy to cause data confusion and data security problems, which is called thread safety problem.
Under what circumstances will thread safety problems occur?
Multiple threads share the same resource
And at least one thread is performing the write operation
Example: saving money and withdrawing money
There are two threads: saving and withdrawing.
Save money and withdraw money
Thread 1 balance thread 2
1000 "- 1000
1000 "1000 -" 2000
1000 "- 500"
Correct: the balance at the end should be 1500, not 500,
The problem of buying tickets
There are 2 threads to sell tickets.
Sell tickets
Thread 1 votes Thread 2
1000 "- 1000
1000-1-"999
999 "- 1000-1
Correct: the balance at the end should be 998, not 999
Ticket purchase error (non-thread synchronization) instance:
Public class love implements Runnable {private int piao=3000;// has 3000 tickets public boolean sale () {/ / ture represents there are still tickets; false reps have no tickets if (piao1;} public void run () {while (sale ()); / / cycle execution; until the tickets are sold out and return false} public class Main {public static void main (String [] a) {love tjlove = new love (); for (int item1tI)
