How to use the "CONCURRENT" framework in the Java library to achieve thread security?
How to use the "CONCURRENT" framework in the Java library to achieve thread security?
introduction:
In multi -threaded programming, thread security is a very important concept.Thread security means that when multiple threads access to a shared resource at the same time, it is guaranteed that the resource can be correctly accessed and there will be no inconsistent data or other abnormalities.In the Java class library, a "Concurrent" framework provides us with some tool categories and interfaces to help us achieve thread security.
1. Parallelism collection
Java provides some concurrent collection classes, which are safe thread and can efficiently support concurrency operations.Here are some commonly used concurrent collection classes:
1. ConcurrenThashMap: It is a thread -safe hash table, which can be used to replace Hashtable and synchronized HashMap.Its performance is very good and can support high -concurrency reading and writing operations.
Example code:
ConcurrentHashMap<String, Integer> map = new ConcurrentHashMap<>();
map.put("key1", 1);
map.put("key2", 2);
map.put("key3", 3);
int value = map.get("key1");
System.out.println(value);
2. CopyOnWritearrayList: It is an ARRAYList implementation of a thread safe. When writing operations, a new array will be created to store data to avoid read and write conflicts.It is very suitable for reading operations with very frequent and very little operations.
Example code:
CopyOnWriteArrayList<Integer> list = new CopyOnWriteArrayList<>();
list.add(1);
list.add(2);
list.add(3);
for (Integer num: list) {
System.out.println(num);
}
Second, synchronous tool class
In addition to the concurrent collection class, Java's "Concurrent" framework also provides some synchronous tool classes to help us achieve thread security.
1. Countdownlatch: It is a synchronous tool class that allows one or more threads to wait for the execution of other threads.When a thread calls the AWAIT method of the countdownlatch, it will block until the counter is reduced to 0 to continue executing.
Example code:
CountDownLatch latch = new CountDownLatch(2);
new Thread(() -> {
System.out.println ("Sub -thread 1 starts to execute");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
latch.countDown();
}
}).start();
new Thread(() -> {
System.out.println ("Sub -thread 2 starts to execute");
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
latch.countDown();
}
}).start();
try {
System.out.println ("The main thread is waiting for sub -thread execution");
latch.await();
System.out.println ("Sub -thread execution");
} catch (InterruptedException e) {
e.printStackTrace();
}
2. SEMAPHORE: It is a synchronous tool class that can control the number of threads that access a certain resource at the same time.SEMAPHORE can be used to limit or control the number of access resources.
Example code:
Semaphore semaphore = new Semaphore(2);
new Thread(() -> {
try {
semaphore.acquire();
System.out.println ("Thread 1 Get the License");
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
semaphore.release();
System.out.println ("Thread 1 releases the license");
}
}).start();
new Thread(() -> {
try {
semaphore.acquire();
System.out.println ("thread 2 gets permits");
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
semaphore.release();
System.out.println ("Thread 2 releases the license");
}
}).start();
3. Atomic operation
Java's "Concurrent" framework also provides some atomic operation classes that can achieve thread -safe atomic operations.
1. AtomicBoolean: It is an atomic operation class that can perform atomic operations on a Boolean type variable.
Example code:
AtomicBoolean flag = new AtomicBoolean(true);
System.out.println(flag.get());
flag.compareAndSet(true, false);
System.out.println(flag.get());
2. Atomicinteger: It is an atomic operation class that can perform atomic operations on a variable of an INT type.
Example code:
AtomicInteger count = new AtomicInteger(0);
System.out.println(count.get());
count.incrementAndGet();
System.out.println(count.get());
Summarize:
By using the concurrent collection class, synchronization tool classes and atomic operating classes provided by the "CONCURRENT" framework in the Java class library, we can easily implement thread security programming.In multi -threaded programming, it is very important to ensure thread security. It can avoid inconsistent data and other abnormalities. At the same time, it can also improve the performance of the program.Therefore, when writing a multi -threaded program, we should make full use of the "Concurrent" framework in the Java class library to achieve thread security.
