fix code

hutool-core/src/main/java/cn/hutool/core/collection/MemorySafeLinkedBlockingQueue.java

@@ -0,0 +1,132 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package cn.hutool.core.collection;
+
+import cn.hutool.core.thread.SimpleScheduler;
+import cn.hutool.core.util.RuntimeUtil;
+
+import java.util.Collection;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * 内存安全的{@link LinkedBlockingQueue}，可以解决OOM问题。<br>
+ * 原理是通过Runtime#freeMemory()获取剩余内存，当剩余内存低于指定的阈值时，不再加入。
+ *
+ * <p>
+ * 此类来自于：<a href="https://github.com/apache/incubator-shenyu/blob/master/shenyu-common/src/main/java/org/apache/shenyu/common/concurrent/MemorySafeLinkedBlockingQueue.java">
+ * Apache incubator-shenyu</a>
+ * </p>
+ *
+ * @author incubator-shenyu
+ * @since 6.0.0
+ */
+public class MemorySafeLinkedBlockingQueue<E> extends LinkedBlockingQueue<E> {
+	private static final long serialVersionUID = 8032578371749960142L;
+
+	private long maxFreeMemory;
+
+	/**
+	 * 构造
+	 *
+	 * @param maxFreeMemory 最大剩余内存大小，当实际内存小于这个值时，不再加入元素
+	 */
+	public MemorySafeLinkedBlockingQueue(final long maxFreeMemory) {
+		super(Integer.MAX_VALUE);
+		this.maxFreeMemory = maxFreeMemory;
+	}
+
+	/**
+	 * 构造
+	 *
+	 * @param c             初始集合
+	 * @param maxFreeMemory 最大剩余内存大小，当实际内存小于这个值时，不再加入元素
+	 */
+	public MemorySafeLinkedBlockingQueue(final Collection<? extends E> c,
+										 final long maxFreeMemory) {
+		super(c);
+		this.maxFreeMemory = maxFreeMemory;
+	}
+
+	/**
+	 * set the max free memory.
+	 *
+	 * @param maxFreeMemory the max free memory
+	 */
+	public void setMaxFreeMemory(final int maxFreeMemory) {
+		this.maxFreeMemory = maxFreeMemory;
+	}
+
+	/**
+	 * get the max free memory.
+	 *
+	 * @return the max free memory limit
+	 */
+	public long getMaxFreeMemory() {
+		return maxFreeMemory;
+	}
+
+	/**
+	 * determine if there is any remaining free memory.<br>
+	 * 剩余内存是否大于给定阈值
+	 *
+	 * @return {@code true}则表示大于阈值，可以加入元素，否则无法加入
+	 */
+	public boolean hasRemainedMemory() {
+		return FreeMemoryCalculator.INSTANCE.getResult() > maxFreeMemory;
+	}
+
+	@Override
+	public void put(final E e) throws InterruptedException {
+		if (hasRemainedMemory()) {
+			super.put(e);
+		}
+	}
+
+	@Override
+	public boolean offer(final E e, final long timeout, final TimeUnit unit) throws InterruptedException {
+		return hasRemainedMemory() && super.offer(e, timeout, unit);
+	}
+
+	@Override
+	public boolean offer(final E e) {
+		return hasRemainedMemory() && super.offer(e);
+	}
+
+	/**
+	 * 获取内存剩余大小的定时任务
+	 */
+	private static class FreeMemoryCalculator extends SimpleScheduler<Long> {
+		private static final FreeMemoryCalculator INSTANCE = new FreeMemoryCalculator();
+
+		FreeMemoryCalculator() {
+			super(new SimpleScheduler.Job<Long>() {
+				private volatile long maxAvailable;
+
+				@Override
+				public Long getResult() {
+					return this.maxAvailable;
+				}
+
+				@Override
+				public void run() {
+					this.maxAvailable = RuntimeUtil.getFreeMemory();
+				}
+			}, 50);
+		}
+	}
+}

hutool-core/src/main/java/cn/hutool/core/date/SystemClock.java

@@ -12,8 +12,8 @@ import java.util.concurrent.TimeUnit;
  * System.currentTimeMillis()之所以慢是因为去跟系统打了一次交道
  * 后台定时更新时钟，JVM退出时，线程自动回收
  *
- * see： http://git.oschina.net/yu120/sequence
- * @author lry,looly
+ * see： <a href="http://git.oschina.net/yu120/sequence">http://git.oschina.net/yu120/sequence</a>
+ * @author lry, looly
  */
 public class SystemClock {
 

hutool-core/src/main/java/cn/hutool/core/thread/SimpleScheduler.java

@@ -0,0 +1,69 @@
+package cn.hutool.core.thread;
+
+import cn.hutool.core.util.RuntimeUtil;
+
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+
+/**
+ * 简单单线程任务调度器<br>
+ * 通过自定义Job定时执行任务，通过{@link #getResult()} 可以获取调取时的执行结果
+ *
+ * @param <T> 结果类型
+ */
+public class SimpleScheduler<T> {
+	private final Job<T> job;
+
+	/**
+	 * 构造
+	 *
+	 * @param job    任务
+	 * @param period 任务间隔，单位毫秒
+	 */
+	public SimpleScheduler(final Job<T> job, final long period) {
+		this(job, 0, period, true);
+	}
+
+	/**
+	 * 构造
+	 *
+	 * @param job                   任务
+	 * @param initialDelay          初始延迟，单位毫秒
+	 * @param period                执行周期，单位毫秒
+	 * @param fixedRateOrFixedDelay {@code true}表示fixedRate模式，{@code false}表示fixedDelay模式
+	 */
+	public SimpleScheduler(final Job<T> job, final long initialDelay, final long period, final boolean fixedRateOrFixedDelay) {
+		this.job = job;
+
+		final ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor();
+		// 启动定时任务
+		ThreadUtil.schedule(scheduler, job, initialDelay, period, fixedRateOrFixedDelay);
+		// 定时任务在程序结束时结束
+		RuntimeUtil.addShutdownHook(scheduler::shutdown);
+	}
+
+	/**
+	 * 获取执行任务的阶段性结果
+	 *
+	 * @return 结果
+	 */
+	public T getResult() {
+		return this.job.getResult();
+	}
+
+	/**
+	 * 带有结果计算的任务<br>
+	 * 用户实现此接口，通过{@link #run()}实现定时任务的内容，定时任务每次执行或多次执行都可以产生一个结果<br>
+	 * 这个结果存储在一个volatile的对象属性中，通过{@link #getResult()}来读取这一阶段的结果。
+	 *
+	 * @param <T> 结果类型
+	 */
+	public interface Job<T> extends Runnable {
+		/**
+		 * 获取执行结果
+		 *
+		 * @return 执行结果
+		 */
+		T getResult();
+	}
+}

hutool-core/src/main/java/cn/hutool/core/thread/ThreadUtil.java

@@ -9,6 +9,7 @@ import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Future;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.RejectedExecutionHandler;
+import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledThreadPoolExecutor;
 import java.util.concurrent.ThreadFactory;
 import java.util.concurrent.ThreadPoolExecutor;
@@ -114,7 +115,7 @@ public class ThreadUtil {
 	 * Blocking Coefficient(阻塞系数) = 阻塞时间／（阻塞时间+使用CPU的时间）<br>
 	 * 计算密集型任务的阻塞系数为0，而IO密集型任务的阻塞系数则接近于1。
 	 * <p>
-	 * see: http://blog.csdn.net/partner4java/article/details/9417663
+	 * see: <a href="http://blog.csdn.net/partner4java/article/details/9417663">http://blog.csdn.net/partner4java/article/details/9417663</a>
 	 *
 	 * @param blockingCoefficient 阻塞系数，阻塞因子介于0~1之间的数，阻塞因子越大，线程池中的线程数越多。
 	 * @return {@link ThreadPoolExecutor}
@@ -660,10 +661,10 @@ public class ThreadUtil {
 	 * @param initialDelay          初始延迟，单位毫秒
 	 * @param period                执行周期，单位毫秒
 	 * @param fixedRateOrFixedDelay {@code true}表示fixedRate模式，{@code false}表示fixedDelay模式
-	 * @return {@link ScheduledThreadPoolExecutor}
+	 * @return {@link ScheduledExecutorService}
 	 * @since 5.5.8
 	 */
-	public static ScheduledThreadPoolExecutor schedule(final ScheduledThreadPoolExecutor executor,
+	public static ScheduledExecutorService schedule(final ScheduledExecutorService executor,
 													   final Runnable command,
 													   final long initialDelay,
 													   final long period,
@@ -685,10 +686,10 @@ public class ThreadUtil {
 	 * @param period                执行周期
 	 * @param timeUnit              时间单位
 	 * @param fixedRateOrFixedDelay {@code true}表示fixedRate模式，{@code false}表示fixedDelay模式
-	 * @return {@link ScheduledThreadPoolExecutor}
+	 * @return {@link ScheduledExecutorService}
 	 * @since 5.6.5
 	 */
-	public static ScheduledThreadPoolExecutor schedule(ScheduledThreadPoolExecutor executor,
+	public static ScheduledExecutorService schedule(ScheduledExecutorService executor,
 													   final Runnable command,
 													   final long initialDelay,
 													   final long period,

hutool-core/src/test/java/cn/hutool/core/collection/MemorySafeLinkedBlockingQueueTest.java

@@ -0,0 +1,13 @@
+package cn.hutool.core.collection;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class MemorySafeLinkedBlockingQueueTest {
+
+	@Test
+	public void offerTest(){
+		final MemorySafeLinkedBlockingQueue<String> queue = new MemorySafeLinkedBlockingQueue<>(Integer.MAX_VALUE);
+		Assert.assertFalse(queue.offer("123"));
+	}
+}

hutool-core/src/test/java/cn/hutool/core/thread/SimpleSchedulerTest.java

@@ -0,0 +1,37 @@
+package cn.hutool.core.thread;
+
+import cn.hutool.core.io.FileUtil;
+import cn.hutool.core.lang.Console;
+import cn.hutool.core.util.RuntimeUtil;
+
+/**
+ * 简单定时任务测试
+ */
+public class SimpleSchedulerTest {
+	public static void main(final String[] args) {
+
+		// 新建一个定时任务，定时获取内存信息
+		final SimpleScheduler<Long> scheduler = new SimpleScheduler<>(new SimpleScheduler.Job<Long>() {
+			private volatile long maxAvailable;
+
+			@Override
+			public Long getResult() {
+				return this.maxAvailable;
+			}
+
+			@Override
+			public void run() {
+				this.maxAvailable = RuntimeUtil.getFreeMemory();
+			}
+		}, 50);
+
+		// 另一个线程不停获取内存结果计算值
+		ThreadUtil.execAsync(() -> {
+			//noinspection InfiniteLoopStatement
+			while (true) {
+				Console.log(FileUtil.readableFileSize(scheduler.getResult()));
+				ThreadUtil.sleep(1000);
+			}
+		});
+	}
+}