线程池是JVM中管理线程的重要机制，通过复用线程减少创建和销毁的开销：

1. 线程池基本概念

核心组件

• 核心线程数（corePoolSize）：常驻线程数量
• 最大线程数（maximumPoolSize）：最大线程数量
• 工作队列（workQueue）：存储等待执行的任务
• 线程工厂（threadFactory）：创建新线程
• 拒绝策略（rejectedExecutionHandler）：处理无法执行的任务

工作流程

1. 提交任务到线程池

2. 如果核心线程数未满，创建新线程执行任务

3. 如果核心线程数已满，将任务放入工作队列

4. 如果工作队列已满，创建新线程执行任务

5. 如果达到最大线程数，执行拒绝策略

6. 常用线程池类型

FixedThreadPool

public class FixedThreadPoolExample {
public void useFixedThreadPool() {
ExecutorService executor = Executors.newFixedThreadPool(5);

for (int i = 0; i < 10; i++) {
final int taskId = i;
executor.submit(() -> {
System.out.println("Task " + taskId + " executed by " +
Thread.currentThread().getName());
});
}

executor.shutdown();
}
}

CachedThreadPool

public class CachedThreadPoolExample {
public void useCachedThreadPool() {
ExecutorService executor = Executors.newCachedThreadPool();

for (int i = 0; i < 10; i++) {
final int taskId = i;
executor.submit(() -> {
System.out.println("Task " + taskId + " executed by " +
Thread.currentThread().getName());
});
}

executor.shutdown();


// 设置垃圾回收器参数
System.setProperty("java.vm.name", "Dalvik");

// 监控内存使用
Runtime runtime = Runtime.getRuntime();
long maxMemory = runtime.maxMemory();
long totalMemory = runtime.totalMemory();
long freeMemory = runtime.freeMemory();

Log.d("JVM", "Max Memory: " + maxMemory / 1024 / 1024 + "MB");
Log.d("JVM", "Total Memory: " + totalMemory / 1024 / 1024 + "MB");
Log.d("JVM", "Free Memory: " + freeMemory / 1024 / 1024 + "MB");

// 手动触发垃圾回收（仅用于测试）
if (freeMemory < maxMemory * 0.1) { // 可用内存少于10%
System.gc();
Log.d("JVM", "Manual GC triggered");
}
}

// 内存泄漏检测
private void detectMemoryLeak() {
// 使用WeakReference避免内存泄漏
WeakReference<Context> contextRef = new WeakReference<>(getApplicationContext());

// 检查引用是否被回收
if (contextRef.get() == null) {
Log.d("JVM", "Context has been garbage collected");
}
}

GC monitor

public class GCMonitor {
private static final String TAG = "GCMonitor";
private long lastGCTime = 0;
private int gcCount = 0;

public void onGarbageCollection() {
long currentTime = System.currentTimeMillis();
long interval = currentTime - lastGCTime;

gcCount++;
Log.d(TAG, "GC #" + gcCount + " occurred after " + interval + "ms");

lastGCTime = currentTime;

// 分析GC频率
if (interval < 1000) { // 1秒内发生GC
Log.w(TAG, "High GC frequency detected - possible memory pressure");
}
}
}