提取想要的apk， 例如CM ROM包中的含天气的时钟不错！
并发
线程池
- ExecutorService
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21public class ConcurrencyMain {
public static void main(String[] args) throws InterruptedException {
ExecutorService executor = Executors.newWorkStealingPool();
List<Callable<String>> callables = Arrays.asList(
() -> "task1",
() -> "task2",
() -> "task3");
executor.invokeAll(callables)
.stream()
.map(future -> {
try {
return future.get();
} catch (Exception e) {
throw new IllegalStateException(e);
}
})
.forEach(System.out::println);
}
} - ScheduledExecutorService区别 两者的区别是
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13public class ConcurrencyMain {
public static void main(String[] args) throws InterruptedException {
ScheduledExecutorService executor = Executors.newScheduledThreadPool(3);
ScheduledFuture<?> future = executor.schedule(() -> System.out.println("执行延迟任务"), 2, TimeUnit.SECONDS);
TimeUnit.MILLISECONDS.sleep(1000);
long remainingDelay = future.getDelay(TimeUnit.MILLISECONDS);
System.out.println(String.format("剩余延迟时间: %sms", remainingDelay));
}
}ScheduledExecutorService是可延迟执行。
同步(Synchronized)
对象锁
语法:1
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38public class SynchronizedMain {
public static void main(String[] args) {
// ==[测试一:同一对象]==
// 结果: 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
Test t1 = new Test();
Thread runnable1 = new Thread(() -> t1.exec());
Thread runnable2 = new Thread(() -> t1.exec());
runnable1.start();
runnable2.start();
// ==[测试二:不同一对象]==
// 结果: 0 0 1 2 3 4 5 6 7 1 2 3 4 5 6 7 8 9 8 9
Test t2 = new Test();
Thread runnable3 = new Thread(() -> t1.exec());
Thread runnable4 = new Thread(() -> t2.exec());
runnable3.start();
runnable4.start();
}
}
// 以下两种方式等价，仅作用范围不一样。
class Test {
public synchronized void exec() {
for (int i = 0; i < 10; i++) {
System.out.printf(i + " ");
}
}
public void exec() {
synchronized (this) {
for (int i = 0; i < 10; i++) {
System.out.printf(i + " ");
}
}
}
}结论: 同一对象调用该方法是锁定的，不同对象不会进行锁定。
类锁
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40public class SynchronizedMain {
public static void main(String[] args) {
// ==[测试一:同一对象]==
// 结果: 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
Test t1 = new Test();
Thread runnable1 = new Thread(() -> t1.exec());
Thread runnable2 = new Thread(() -> t1.exec());
runnable1.start();
runnable2.start();
// ==[测试二:不同一对象]==
// 结果: 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
Test t2 = new Test();
Thread runnable3 = new Thread(() -> t1.exec());
Thread runnable4 = new Thread(() -> t2.exec());
runnable3.start();
runnable4.start();
}
}
// 以下两种方式等价
class Test {
private static Object lock = new Object();
public void exec() {
synchronized (lock) {
for (int i = 0; i < 10; i++) {
System.out.printf(i + " ");
}
}
}
public void exec() {
synchronized (Test.class) {
for (int i = 0; i < 10; i++) {
System.out.printf(i + " ");
}
}
}
}结论: 该方式锁的作用范围是整个类。
指定锁
语法:1
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32public class SynchronizedMain {
private static Object lock = new Object();
public static void main(String[] args) {
// ==[测试一:同一对象]==
// 结果: 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
Test t1 = new Test();
Thread runnable1 = new Thread(() -> t1.exec(lock));
Thread runnable2 = new Thread(() -> t1.exec(lock));
runnable1.start();
runnable2.start();
// ==[测试二:不同一对象]==
// 结果: 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
Test t2 = new Test();
Thread runnable3 = new Thread(() -> t1.exec(lock));
Thread runnable4 = new Thread(() -> t2.exec(lock));
runnable3.start();
runnable4.start();
}
}
class Test {
public void exec(Object lock) {
synchronized (lock) {
for (int i = 0; i < 10; i++) {
System.out.printf(i + " ");
}
}
}
}结论: 该方式取决于传入的锁。当对象属性发生改变时，锁就失去了作用。
对于 Java8 中，ReentrantLock 可实现锁的作用。