---
title: Atomic
category: Java
tag:
- Java
---
## Atomic
Atomic Atomic
/
`java.util.concurrent` `java.util.concurrent.atomic`,
JUC 4
****
- AtomicInteger
- AtomicLong
- AtomicBoolean
****
- AtomicIntegerArray
- AtomicLongArray
- AtomicReferenceArray
****
- AtomicReference
- AtomicMarkableReference boolean ~~ CAS ABA ~~
- AtomicStampedReference CAS ABA
****
- AtomicIntegerFieldUpdater:
- AtomicLongFieldUpdater
- AtomicReferenceFieldUpdater
> ** [issue#626](https://github.com/Snailclimb/JavaGuide/issues/626)** : `AtomicMarkableReference` ABA
```java
/**
AtomicMarkableReferencebooleantruefalse
ABAABA
@author : mazh
@Date : 2020/1/17 14:41
*/
public class SolveABAByAtomicMarkableReference {
private static AtomicMarkableReference atomicMarkableReference = new AtomicMarkableReference(100, false);
public static void main(String[] args) {
Thread refT1 = new Thread(() -> {
try {
TimeUnit.SECONDS.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
atomicMarkableReference.compareAndSet(100, 101, atomicMarkableReference.isMarked(), !atomicMarkableReference.isMarked());
atomicMarkableReference.compareAndSet(101, 100, atomicMarkableReference.isMarked(), !atomicMarkableReference.isMarked());
});
Thread refT2 = new Thread(() -> {
boolean marked = atomicMarkableReference.isMarked();
try {
TimeUnit.SECONDS.sleep(2);
} catch (InterruptedException e) {
e.printStackTrace();
}
boolean c3 = atomicMarkableReference.compareAndSet(100, 101, marked, !marked);
System.out.println(c3); // true,false
});
refT1.start();
refT2.start();
}
}
```
**CAS ABA **
- : x A x A x A x B x A x x A compareAndSet
- ():
- `AtomicInteger`
```java
import java.util.concurrent.atomic.AtomicInteger;
public class AtomicIntegerDefectDemo {
public static void main(String[] args) {
defectOfABA();
}
static void defectOfABA() {
final AtomicInteger atomicInteger = new AtomicInteger(1);
Thread coreThread = new Thread(
() -> {
final int currentValue = atomicInteger.get();
System.out.println(Thread.currentThread().getName() + " ------ currentValue=" + currentValue);
//
try {
Thread.sleep(300);
} catch (InterruptedException e) {
e.printStackTrace();
}
boolean casResult = atomicInteger.compareAndSet(1, 2);
System.out.println(Thread.currentThread().getName()
+ " ------ currentValue=" + currentValue
+ ", finalValue=" + atomicInteger.get()
+ ", compareAndSet Result=" + casResult);
}
);
coreThread.start();
// coreThread
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
Thread amateurThread = new Thread(
() -> {
int currentValue = atomicInteger.get();
boolean casResult = atomicInteger.compareAndSet(1, 2);
System.out.println(Thread.currentThread().getName()
+ " ------ currentValue=" + currentValue
+ ", finalValue=" + atomicInteger.get()
+ ", compareAndSet Result=" + casResult);
currentValue = atomicInteger.get();
casResult = atomicInteger.compareAndSet(2, 1);
System.out.println(Thread.currentThread().getName()
+ " ------ currentValue=" + currentValue
+ ", finalValue=" + atomicInteger.get()
+ ", compareAndSet Result=" + casResult);
}
);
amateurThread.start();
}
}
```
```
Thread-0 ------ currentValue=1
Thread-1 ------ currentValue=1, finalValue=2, compareAndSet Result=true
Thread-1 ------ currentValue=2, finalValue=1, compareAndSet Result=true
Thread-0 ------ currentValue=1, finalValue=2, compareAndSet Result=true
```
##
###
- AtomicInteger
- AtomicLong
- AtomicBoolean
AtomicInteger
**AtomicInteger **
```java
public final int get() //
public final int getAndSet(int newValue)//
public final int getAndIncrement()//
public final int getAndDecrement() //
public final int getAndAdd(int delta) //
boolean compareAndSet(int expect, int update) //update
public final void lazySet(int newValue)//newValue, lazySet
```
### AtomicInteger
```java
import java.util.concurrent.atomic.AtomicInteger;
public class AtomicIntegerTest {
public static void main(String[] args) {
// TODO Auto-generated method stub
int temvalue = 0;
AtomicInteger i = new AtomicInteger(0);
temvalue = i.getAndSet(3);
System.out.println("temvalue:" + temvalue + "; i:" + i);//temvalue:0; i:3
temvalue = i.getAndIncrement();
System.out.println("temvalue:" + temvalue + "; i:" + i);//temvalue:3; i:4
temvalue = i.getAndAdd(5);
System.out.println("temvalue:" + temvalue + "; i:" + i);//temvalue:4; i:9
}
}
```
###
** **
```java
class Test {
private volatile int count = 0;
//count++
public synchronized void increment() {
count++;
}
public int getCount() {
return count;
}
}
```
** **
```java
class Test2 {
private AtomicInteger count = new AtomicInteger();
public void increment() {
count.incrementAndGet();
}
//AtomicInteger
public int getCount() {
return count.get();
}
}
```
### AtomicInteger
AtomicInteger
```java
// setup to use Unsafe.compareAndSwapInt for updates
private static final Unsafe unsafe = Unsafe.getUnsafe();
private static final long valueOffset;
static {
try {
valueOffset = unsafe.objectFieldOffset
(AtomicInteger.class.getDeclaredField("value"));
} catch (Exception ex) { throw new Error(ex); }
}
private volatile int value;
```
AtomicInteger CAS (compare and swap) + volatile native synchronized
CAS UnSafe objectFieldOffset() value volatile JVM
##
###
- AtomicIntegerArray
- AtomicLongArray
- AtomicReferenceArray
AtomicIntegerArray
**AtomicIntegerArray **
```java
public final int get(int i) // index=i
public final int getAndSet(int i, int newValue)// index=i newValue
public final int getAndIncrement(int i)// index=i
public final int getAndDecrement(int i) // index=i
public final int getAndAdd(int i, int delta) // index=i
boolean compareAndSet(int i, int expect, int update) // index=i update
public final void lazySet(int i, int newValue)// index=i newValue, lazySet
```
### AtomicIntegerArray
```java
import java.util.concurrent.atomic.AtomicIntegerArray;
public class AtomicIntegerArrayTest {
public static void main(String[] args) {
// TODO Auto-generated method stub
int temvalue = 0;
int[] nums = { 1, 2, 3, 4, 5, 6 };
AtomicIntegerArray i = new AtomicIntegerArray(nums);
for (int j = 0; j < nums.length; j++) {
System.out.println(i.get(j));
}
temvalue = i.getAndSet(0, 2);
System.out.println("temvalue:" + temvalue + "; i:" + i);
temvalue = i.getAndIncrement(0);
System.out.println("temvalue:" + temvalue + "; i:" + i);
temvalue = i.getAndAdd(0, 5);
System.out.println("temvalue:" + temvalue + "; i:" + i);
}
}
```
##
###
- AtomicReference
- AtomicStampedReference CAS ABA
- AtomicMarkableReference boolean ~~ CAS ABA ~~
AtomicReference
### AtomicReference
```java
import java.util.concurrent.atomic.AtomicReference;
public class AtomicReferenceTest {
public static void main(String[] args) {
AtomicReference ar = new AtomicReference();
Person person = new Person("SnailClimb", 22);
ar.set(person);
Person updatePerson = new Person("Daisy", 20);
ar.compareAndSet(person, updatePerson);
System.out.println(ar.get().getName());
System.out.println(ar.get().getAge());
}
}
class Person {
private String name;
private int age;
public Person(String name, int age) {
super();
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
```
Person Person AtomicReference compareAndSet CAS ar ar person updatePerson AtomicInteger compareAndSet
```
Daisy
20
```
### AtomicStampedReference
```java
import java.util.concurrent.atomic.AtomicStampedReference;
public class AtomicStampedReferenceDemo {
public static void main(String[] args) {
// stamp
final Integer initialRef = 0, initialStamp = 0;
final AtomicStampedReference asr = new AtomicStampedReference(initialRef, initialStamp);
System.out.println("currentValue=" + asr.getReference() + ", currentStamp=" + asr.getStamp());
// compare and set
final Integer newReference = 666, newStamp = 999;
final boolean casResult = asr.compareAndSet(initialRef, newReference, initialStamp, newStamp);
System.out.println("currentValue=" + asr.getReference()
+ ", currentStamp=" + asr.getStamp()
+ ", casResult=" + casResult);
// stamp
int[] arr = new int[1];
final Integer currentValue = asr.get(arr);
final int currentStamp = arr[0];
System.out.println("currentValue=" + currentValue + ", currentStamp=" + currentStamp);
// stamp
final boolean attemptStampResult = asr.attemptStamp(newReference, 88);
System.out.println("currentValue=" + asr.getReference()
+ ", currentStamp=" + asr.getStamp()
+ ", attemptStampResult=" + attemptStampResult);
// stamp
asr.set(initialRef, initialStamp);
System.out.println("currentValue=" + asr.getReference() + ", currentStamp=" + asr.getStamp());
// [] weak compare and set
// weakCompareAndSet compareAndSet [: jdk-8u191]
// "May fail spuriously and does not provide ordering guarantees,
// so is only rarely an appropriate alternative to compareAndSet."
// todo jvm native
final boolean wCasResult = asr.weakCompareAndSet(initialRef, newReference, initialStamp, newStamp);
System.out.println("currentValue=" + asr.getReference()
+ ", currentStamp=" + asr.getStamp()
+ ", wCasResult=" + wCasResult);
}
}
```
```
currentValue=0, currentStamp=0
currentValue=666, currentStamp=999, casResult=true
currentValue=666, currentStamp=999
currentValue=666, currentStamp=88, attemptStampResult=true
currentValue=0, currentStamp=0
currentValue=666, currentStamp=999, wCasResult=true
```
### AtomicMarkableReference
```java
import java.util.concurrent.atomic.AtomicMarkableReference;
public class AtomicMarkableReferenceDemo {
public static void main(String[] args) {
// mark
final Boolean initialRef = null, initialMark = false;
final AtomicMarkableReference amr = new AtomicMarkableReference(initialRef, initialMark);
System.out.println("currentValue=" + amr.getReference() + ", currentMark=" + amr.isMarked());
// compare and set
final Boolean newReference1 = true, newMark1 = true;
final boolean casResult = amr.compareAndSet(initialRef, newReference1, initialMark, newMark1);
System.out.println("currentValue=" + amr.getReference()
+ ", currentMark=" + amr.isMarked()
+ ", casResult=" + casResult);
// mark
boolean[] arr = new boolean[1];
final Boolean currentValue = amr.get(arr);
final boolean currentMark = arr[0];
System.out.println("currentValue=" + currentValue + ", currentMark=" + currentMark);
// mark
final boolean attemptMarkResult = amr.attemptMark(newReference1, false);
System.out.println("currentValue=" + amr.getReference()
+ ", currentMark=" + amr.isMarked()
+ ", attemptMarkResult=" + attemptMarkResult);
// mark
amr.set(initialRef, initialMark);
System.out.println("currentValue=" + amr.getReference() + ", currentMark=" + amr.isMarked());
// [] weak compare and set
// weakCompareAndSet compareAndSet [: jdk-8u191]
// "May fail spuriously and does not provide ordering guarantees,
// so is only rarely an appropriate alternative to compareAndSet."
// todo jvm native
final boolean wCasResult = amr.weakCompareAndSet(initialRef, newReference1, initialMark, newMark1);
System.out.println("currentValue=" + amr.getReference()
+ ", currentMark=" + amr.isMarked()
+ ", wCasResult=" + wCasResult);
}
}
```
```
currentValue=null, currentMark=false
currentValue=true, currentMark=true, casResult=true
currentValue=true, currentMark=true
currentValue=true, currentMark=false, attemptMarkResult=true
currentValue=null, currentMark=false
currentValue=true, currentMark=true, wCasResult=true
```
##
###
- AtomicIntegerFieldUpdater:
- AtomicLongFieldUpdater
- AtomicReferenceFieldUpdater
newUpdater() public volatile
`AtomicIntegerFieldUpdater`
### AtomicIntegerFieldUpdater
```java
import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
public class AtomicIntegerFieldUpdaterTest {
public static void main(String[] args) {
AtomicIntegerFieldUpdater a = AtomicIntegerFieldUpdater.newUpdater(User.class, "age");
User user = new User("Java", 22);
System.out.println(a.getAndIncrement(user));// 22
System.out.println(a.get(user));// 23
}
}
class User {
private String name;
public volatile int age;
public User(String name, int age) {
super();
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
```
```
22
23
```
## Reference
- Java