如何解决Java后端功能开发中的内存泄漏问题？

public class Example {
    private Object obj;

    public void setObject(Object obj) {
        this.obj = obj;
    }

    public Object getObject() {
        return obj;
    }

    public void releaseObject() {
        obj = null;
    }
}

public class Cache {
    private Map<String, Object> cacheMap = new HashMap<>();

    public void put(String key, Object value) {
        cacheMap.put(key, value);
    }

    public Object get(String key) {
        return cacheMap.get(key);
    }

    public void remove(String key) {
        cacheMap.remove(key);
    }
}

public class Example {
    public void processFile(String filename) {
        File file = new File(filename);
        try (FileInputStream fis = new FileInputStream(file)) {
            // 处理文件
        } catch (IOException e) {
            // 异常处理
        }
    }
}

public class Example {
    private List<EventListener> listeners = new ArrayList<>();

    public void addListener(EventListener listener) {
        listeners.add(listener);
    }

    public void removeListener(EventListener listener) {
        listeners.remove(listener);
    }

    public void fireEvent(Event event) {
        for (EventListener listener : listeners) {
            listener.onEvent(event);
        }
    }
}