Java Concurrent Programming 2

Description: First on the code, notes follow-up supplement
public class CoderTest1 {

private static Object key;

public static void Main (string[] args) {

Synchronization container Vector HashTable collections.synchronizedlist ()
If a modification occurs during an iteration, the concurrent modification exception modifies the thread independent copy of a collection (which can result in the inability to get the latest data, which has an effect on efficiency)
/* Multiple threading operations easy to throw arrayindexoutofboundsexception exceptions
* vector<object> Vector = new vector<> ();
int lastsize = Vector.size ()-1;
Vector.remove (lastsize);
* */
vector<object> vector = new vector<> ();
Synchronized (key) {
int lastsize = Vector.size ()-1;
Vector.remove (lastsize);
//        }
This situation can occur with concurrent modification exceptions Concurrentmodificationexception
arraylist<object> list = new arraylist<> ();
List.add (1);
List.add (1);
List.add (1);
List.add (1);
List.add (1);
for (Object obj:list) {
System.out.println (obj);
List.remove (obj);
//        }

Concurrent container CONCURRENTHASHMAP segment lock a lock on each linked list, after 1.8 it seems to be a node lock
Map.putifabsent only key does not exist to operate successfully and will not overwrite
Copyonwritearraylist/set Application Scenario: Read more, write very little
blocking queues
FIFO, block if queue is empty
Concurrenthashmap map = new Concurrenthashmap ();
(map.putifabsent);
Map.putifabsent (1,3);
SYSTEM.OUT.PRINTLN (map);
//
copyonwritearraylist<object> list = new copyonwritearraylist<> ();
Blockingqueue queue = new Arrayblockingqueue (2);

1 Latching 2 Fence 3 signal volume
After you reach the fence, you need all the threads to execute before you can continue executing other threads
Final Countdownlatch latch = new Countdownlatch (2);
First thread
New Thread () {
public void Run () {
try {
SYSTEM.OUT.PRINTLN ("Child Thread" +thread.currentthread (). GetName () + "executing");
Thread.Sleep (3000);
SYSTEM.OUT.PRINTLN ("Child Thread" +thread.currentthread (). GetName () + "execution complete");
Latch.countdown ();
} catch (Interruptedexception e) {
E.printstacktrace ();
//                }
//            }
}.start ();
A second thread
New Thread () {
public void Run () {
try {
SYSTEM.OUT.PRINTLN ("Child Thread" +thread.currentthread (). GetName () + "executing");
Thread.Sleep (3000);
SYSTEM.OUT.PRINTLN ("Child Thread" +thread.currentthread (). GetName () + "execution complete");
Latch.countdown ();
} catch (Interruptedexception e) {
E.printstacktrace ();
//                }
//            }
}.start ();
//
try {
System.out.println ("Wait for two sub-threads to finish executing ... ");
Atresia
Latch.await ();
System.out.println ("Two sub-threads have been executed ... ");
System.out.println ("Continue with the main thread");
} catch (Interruptedexception e) {
E.printstacktrace ();
//        }

int N = 4;
Cyclicbarrier barrier = new Cyclicbarrier (N);
for (int i=0; i<n; i++) {
New Writer (barrier). Start ();
}
int worknum = number of 8;//workers
Semaphore Semaphore = new Semaphore (5);//semaphore, number of machines
for (int i=0; i<worknum; i++) {
New Worker (I,semaphore). Start ();
}
}

For fences
Static class Writer extends thread{
Private Cyclicbarrier Cyclicbarrier;
Public Writer (Cyclicbarrier cyclicbarrier) {
This.cyclicbarrier = Cyclicbarrier;
}
@Override
public void Run () {
SYSTEM.OUT.PRINTLN ("Thread" +thread.currentthread (). GetName () + "writing data ... ");
try {
Thread.Sleep (5000);
SYSTEM.OUT.PRINTLN ("Thread" +thread.currentthread (). GetName () + "write data, wait for other threads to write data ... ");
Cyclicbarrier.await ();
} catch (Interruptedexception e) {
E.printstacktrace ();
} catch (Brokenbarrierexception e) {
E.printstacktrace ();
}
System.out.println ("All threads have finished writing data, continue to perform other tasks ... ");
}
}

For signal volume
Static class Worker extends thread{
private int num;
Private Semaphore Semaphore;
public Worker (int num, Semaphore Semaphore) {
This.num = num;
This.semaphore = semaphore;
}
@Override
public void Run () {
try {
Semaphore.acquire ();
System.out.println ("Worker" +this.num+ "occupies a machine production ... ");
Thread.Sleep (3000);
SYSTEM.OUT.PRINTLN ("Workers" +this.num+ "release the Machine");
Semaphore.release ();
} catch (Interruptedexception e) {
E.printstacktrace ();
}
}
}

}

Java Concurrent Programming 2