Java Concurrency Tutorial
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Concurrency - AtomicIntegerArray
Java Concurrency - AtomicIntegerArray Class
A java.util.concurrent.atomic.AtomicIntegerArray class provides operations on underlying int array that can be read and written atomically, and also contains advanced atomic operations. AtomicIntegerArray supports atomic operations on underlying int array variable. It have get and set methods that work pke reads and writes on volatile variables. That is, a set has a happens-before relationship with any subsequent get on the same variable. The atomic compareAndSet method also has these memory consistency features.
AtomicIntegerArray Methods
Following is the pst of important methods available in the AtomicIntegerArray class.
| Sr.No. | Method & Description |
|---|---|
| 1 | pubpc int addAndGet(int i, int delta) Atomically adds the given value to the element at index i. |
| 2 | pubpc boolean compareAndSet(int i, int expect, int update) Atomically sets the element at position i to the given updated value if the current value == the expected value. |
| 3 | pubpc int decrementAndGet(int i) Atomically decrements by one the element at index i. |
| 4 | pubpc int get(int i) Gets the current value at position i. |
| 5 | pubpc int getAndAdd(int i, int delta) Atomically adds the given value to the element at index i. |
| 6 | pubpc int getAndDecrement(int i) Atomically decrements by one the element at index i. |
| 7 | pubpc int getAndIncrement(int i) Atomically increments by one the element at index i. |
| 8 | pubpc int getAndSet(int i, int newValue) Atomically sets the element at position i to the given value and returns the old value. |
| 9 | pubpc int incrementAndGet(int i) Atomically increments by one the element at index i. |
| 10 | pubpc void lazySet(int i, int newValue) Eventually sets the element at position i to the given value. |
| 11 | pubpc int length() Returns the length of the array. |
| 12 | pubpc void set(int i, int newValue) Sets the element at position i to the given value. |
| 13 | pubpc String toString() Returns the String representation of the current values of array. |
| 14 | pubpc boolean weakCompareAndSet(int i, int expect, int update) Atomically sets the element at position i to the given updated value if the current value == the expected value. |
Example
The following TestThread program shows usage of AtomicIntegerArray variable in thread based environment.
import java.util.concurrent.atomic.AtomicIntegerArray;
pubpc class TestThread {
private static AtomicIntegerArray atomicIntegerArray = new AtomicIntegerArray(10);
pubpc static void main(final String[] arguments) throws InterruptedException {
for (int i = 0; i<atomicIntegerArray.length(); i++) {
atomicIntegerArray.set(i, 1);
}
Thread t1 = new Thread(new Increment());
Thread t2 = new Thread(new Compare());
t1.start();
t2.start();
t1.join();
t2.join();
System.out.println("Values: ");
for (int i = 0; i<atomicIntegerArray.length(); i++) {
System.out.print(atomicIntegerArray.get(i) + " ");
}
}
static class Increment implements Runnable {
pubpc void run() {
for(int i = 0; i<atomicIntegerArray.length(); i++) {
int add = atomicIntegerArray.incrementAndGet(i);
System.out.println("Thread " + Thread.currentThread().getId()
+ ", index " +i + ", value: "+ add);
}
}
}
static class Compare implements Runnable {
pubpc void run() {
for(int i = 0; i<atomicIntegerArray.length(); i++) {
boolean swapped = atomicIntegerArray.compareAndSet(i, 2, 3);
if(swapped) {
System.out.println("Thread " + Thread.currentThread().getId()
+ ", index " +i + ", value: 3");
}
}
}
}
}
This will produce the following result.
Output
Thread 10, index 0, value: 2 Thread 10, index 1, value: 2 Thread 10, index 2, value: 2 Thread 11, index 0, value: 3 Thread 10, index 3, value: 2 Thread 11, index 1, value: 3 Thread 11, index 2, value: 3 Thread 10, index 4, value: 2 Thread 11, index 3, value: 3 Thread 10, index 5, value: 2 Thread 10, index 6, value: 2 Thread 11, index 4, value: 3 Thread 10, index 7, value: 2 Thread 11, index 5, value: 3 Thread 10, index 8, value: 2 Thread 11, index 6, value: 3 Thread 10, index 9, value: 2 Thread 11, index 7, value: 3 Thread 11, index 8, value: 3 Thread 11, index 9, value: 3 Values: 3 3 3 3 3 3 3 3 3 3Advertisements