// 不推薦的方式
public void readFile(String path) throws IOException {
    FileInputStream fis = new FileInputStream(path);
    // 使用fis讀取文件
    // 如果這里發(fā)生異常，fis可能不會被關閉
}

// 推薦的方式：使用try-with-resources
public void readFile(String path) throws IOException {
    try (FileInputStream fis = new FileInputStream(path)) {
        // 使用fis讀取文件
    } // fis會自動關閉，即使發(fā)生異常
}

public class CacheManager {
    // 靜態(tài)集合可能導致內(nèi)存泄漏
    private static final Map<String, Object> cache = new HashMap<>();
    
    public static void addToCache(String key, Object value) {
        cache.put(key, value);
    }
    
    // 確保提供清理機制
    public static void removeFromCache(String key) {
        cache.remove(key);
    }
    
    public static void clearCache() {
        cache.clear();
    }
}

public class Outer {
    private byte[] data = new byte[100000]; // 大對象
    
    // 不推薦：非靜態(tài)內(nèi)部類
    public class Inner {
        public void process() {
            System.out.println(data.length);
        }
    }
    
    // 推薦：靜態(tài)內(nèi)部類
    public static class StaticInner {
        private final Outer outer;
        
        public StaticInner(Outer outer) {
            this.outer = outer;
        }
        
        public void process() {
            System.out.println(outer.data.length);
        }
    }
}

public class Person {
    private String name;
    private int age;
    
    // 構造函數(shù)、getter和setter省略
    
    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Person person = (Person) o;
        return age == person.age && Objects.equals(name, person.name);
    }
    
    @Override
    public int hashCode() {
        return Objects.hash(name, age);
    }
}

public class ImageCache {
    // 使用WeakHashMap，當鍵不再被引用時，對應的條目會被自動移除
    private final Map<String, WeakReference<BufferedImage>> cache = new WeakHashMap<>();
    
    public BufferedImage getImage(String path) {
        WeakReference<BufferedImage> reference = cache.get(path);
        BufferedImage image = (reference != null) ? reference.get() : null;
        
        if (image == null) {
            image = loadImage(path);
            cache.put(path, new WeakReference<>(image));
        }
        
        return image;
    }
    
    private BufferedImage loadImage(String path) {
        // 加載圖片的代碼
        return null; // 實際應用中返回加載的圖片
    }
}

// 不推薦
public class ResourceHolder {
    private FileInputStream fis;
    
    public ResourceHolder(String path) throws IOException {
        fis = new FileInputStream(path);
    }
    
    @Override
    protected void finalize() throws Throwable {
        if (fis != null) {
            fis.close();
        }
        super.finalize();
    }
}

???????// 推薦：實現(xiàn)AutoCloseable接口
public class ResourceHolder implements AutoCloseable {
    private FileInputStream fis;
    
    public ResourceHolder(String path) throws IOException {
        fis = new FileInputStream(path);
    }
    
    @Override
    public void close() throws IOException {
        if (fis != null) {
            fis.close();
            fis = null;
        }
    }
}

public class ThreadLocalExample {
    // 定義ThreadLocal變量
    private static final ThreadLocal<byte[]> threadLocalBuffer = 
        ThreadLocal.withInitial(() -> new byte[1024 * 1024]); // 1MB buffer
    
    public void process() {
        // 使用ThreadLocal變量
        byte[] buffer = threadLocalBuffer.get();
        // 處理邏輯...
        
        // 重要：使用完畢后清理ThreadLocal變量
        threadLocalBuffer.remove();
    }
}

// 潛在問題：Parent和Child相互引用
public class Parent {
    private List<Child> children = new ArrayList<>();
    
    public void addChild(Child child) {
        children.add(child);
        child.setParent(this);
    }
}

public class Child {
    private Parent parent;
    
    public void setParent(Parent parent) {
        this.parent = parent;
    }
}

???????// 解決方案：使用弱引用打破循環(huán)
public class Child {
    private WeakReference<Parent> parentRef;
    
    public void setParent(Parent parent) {
        this.parentRef = new WeakReference<>(parent);
    }
    
    public Parent getParent() {
        return (parentRef != null) ? parentRef.get() : null;
    }
}

// 在關鍵點手動觸發(fā)垃圾回收和內(nèi)存使用情況打?。▋H用于開發(fā)和調(diào)試）
System.gc();
Runtime runtime = Runtime.getRuntime();
long usedMemory = runtime.totalMemory() - runtime.freeMemory();
System.out.println("Used Memory: " + (usedMemory / 1024 / 1024) + " MB");