Java导致内存泄漏的多种情况分析

public class FileTest {
    public static void main(String[] args) {
        FileInputStream fis = null;
        try {
            fis = new FileInputStream("test.txt");
            // 读取文件，未调用 fis.close()
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } finally {
            // 未调用 fis.close() → fis 持有 Native 引用，无法回收
        }
    }
}

public class ThreadLocalTest {
    private static ThreadLocal<User> userThreadLocal = new ThreadLocal<>();
    public static void main(String[] args) {
        // 线程池（核心线程长期存活）
        TThreadPoolExecutor executor = new ThreadPoolExecutor(
                2,
                4,
                10,
                TimeUnit.SECONDS,
                new ArrayBlockingQueue<>(100),
                new ThreadFactoryBuilder().setNameFormat("my-thread-pool-%d").setDaemon(false).setPriority(Thread.NORM_PRIORITY).build(),
                new ThreadPoolExecutor.AbortPolicy()
        );
        executor.submit(() -> {
            User user = new User("李四", 30);
            userThreadLocal.set(user); // 存储到 ThreadLocal
            // 业务执行完毕，未调用 remove()
            // 核心线程不会销毁，ThreadLocal 仍持有 user 引用
        });
    }
}

public class OuterClass {
    private byte[] bigData = new byte[1024 * 1024 * 10]; // 10MB 大对象
    // 非静态内部类
    class InnerClass {
        // 内部类隐式持有 OuterClass 引用
    }
    public InnerClass createInner() {
        return new InnerClass();
    }
    public static void main(String[] args) {
        OuterClass outer = new OuterClass();
        InnerClass inner = outer.createInner();
        // 置空外部类引用，但 inner 仍持有 outer 引用
        outer = null;
        // 若 inner 被静态变量/线程长期持有 → outer 对象（含 bigData）无法回收
    }
}