Java 多线程四：锁二

发布时间：2023-04-15 11:21:06 所属栏目：教程来源：

导读：需要实际测试一下。

示例代码见：

package git.snippets.juc;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.LongAdder;
/**
* 对比AddByAdder, AddByAtomic, Add

需要实际测试一下。

示例代码见：

package git.snippets.juc;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.LongAdder;
/**
* 对比AddByAdder, AddByAtomic, AddBySync几个程序，在数据量比较大的情况下，AddByAdder的效率最高
*/
public class AddWays {
public static void main(String[] args) {
addBySync();
addByAtomicLong();
addByLongAdder();
}
// 使用AtomicLong
public static void addByAtomicLong() {
AtomicLong count = new AtomicLong(0);
Thread[] all = new Thread[1000];
AddWays t = new AddWays();
for (int i = 0; i < all.length; i++) {
all[i] = new Thread(() -> {
for (int j = 0; j < 1000000; j++) {
count.incrementAndGet();
}
});
}
long start = System.currentTimeMillis();
for (Thread thread : all) {
thread.start();
}
for (Thread thread : all) {
try {
thread.join();
} catch (InterruptedException e) {
e.printstacktrace();
}
}
long end = System.currentTimeMillis();
System.out.println("result is " + count.get() + " time is " + (end - start) + "ms (by AtomicLong)");
}
// 使用LongAdder
public static void addByLongAdder() {
Thread[] all = new Thread[1000];
LongAdder count = new LongAdder();
for (int i = 0; i < all.length; i++) {
all[i] = new Thread(() -> {
for (int j = 0; j < 1000000; j++) {
count.increment();
}
});
}
long start = System.currentTimeMillis();
for (Thread thread : all) {
thread.start();
}
for (Thread thread : all) {
try {
thread.join();
} catch (InterruptedException e) {
e.printstacktrace();
}
}
long end = System.currentTimeMillis();
System.out.println("result is " + count + " time is " + (end - start) + "ms (by LongAdder)");
}
static long count = 0;
public static void addBySync() {
Thread[] all = new Thread[1000];
Object o = new Object();
for (int i = 0; i < all.length; i++) {
all[i] = new Thread(() -> {
for (int j = 0; j < 1000000; j++) {
synchronized (o) {
count++;
}
}
});
}
long start = System.currentTimeMillis();
for (Thread thread : all) {
thread.start();
}
for (Thread thread : all) {
try {
thread.join();
} catch (InterruptedException e) {
e.printstacktrace();
}
}
long end = System.currentTimeMillis();
System.out.println("result is " + count + " time is " + (end - start) + "ms (by synchronized)");
}
}
Java SE 11 下，运行得到的执行结果是：

result is 1000000000 time is 10035ms (by synchronized)
result is 1000000000 time is 15818ms (by AtomicLong)
result is 1000000000 time is 963ms (by LongAdder)

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