volatile
关键字只保证了元素的可见性，即对变量的修改各个线程都会立即得到修改后的值采用synchronized：
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public
class
Test {
public
int
inc =
0
;
public
synchronized
void
increase() {
inc++;
}
public
static
void
main(String[] args) {
final
Test test =
new
Test();
for
(
int
i=
0
;i<
10
;i++){
new
Thread(){
public
void
run() {
for
(
int
j=
0
;j<
1000
;j++)
test.increase();
};
}.start();
}
while
(Thread.activeCount()>
1
)
//保证前面的线程都执行完
Thread.yield();
System.out.println(test.inc);
}
}
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采用Lock：
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public
class
Test {
public
int
inc =
0
;
Lock lock =
new
ReentrantLock();
public
void
increase() {
lock.lock();
try
{
inc++;
}
finally
{
lock.unlock();
}
}
public
static
void
main(String[] args) {
final
Test test =
new
Test();
for
(
int
i=
0
;i<
10
;i++){
new
Thread(){
public
void
run() {
for
(
int
j=
0
;j<
1000
;j++)
test.increase();
};
}.start();
}
while
(Thread.activeCount()>
1
)
//保证前面的线程都执行完
Thread.yield();
System.out.println(test.inc);
}
}
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采用AtomicInteger：
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public
class
Test {
public
AtomicInteger inc =
new
AtomicInteger();
public
void
increase() {
inc.getAndIncrement();
}
public
static
void
main(String[] args) {
final
Test test =
new
Test();
for
(
int
i=
0
;i<
10
;i++){
new
Thread(){
public
void
run() {
for
(
int
j=
0
;j<
1000
;j++)
test.increase();
};
}.start();
}
while
(Thread.activeCount()>
1
)
//保证前面的线程都执行完
Thread.yield();
System.out.println(test.inc);
}
}
|