建構穩定可靠的快取系統：Java快取機制的設計與實作經驗分享

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;

public class InMemoryCache<T> {
    private final Map<String, CacheEntry<T>> cache;
    private final long expirationTime;

    private static class CacheEntry<T> {
        private final T value;
        private final long createTime;

        CacheEntry(T value) {
            this.value = value;
            this.createTime = System.currentTimeMillis();
        }

        boolean isExpired(long expirationTime) {
            return System.currentTimeMillis() - createTime > expirationTime;
        }
    }

    public InMemoryCache(long expirationTime) {
        this.cache = new HashMap<>();
        this.expirationTime = expirationTime;
    }

    public void put(String key, T value) {
        cache.put(key, new CacheEntry<>(value));
    }

    public T get(String key) {
        CacheEntry<T> entry = cache.get(key);
        if (entry != null && !entry.isExpired(expirationTime)) {
            return entry.value;
        } else {
            cache.remove(key);
            return null;
        }
    }

    public static void main(String[] args) {
        InMemoryCache<String> cache = new InMemoryCache<>(TimeUnit.MINUTES.toMillis(30));
        cache.put("key1", "value1");
        String value = cache.get("key1");
        System.out.println(value);
    }
}

import java.io.*;
import java.util.HashMap;
import java.util.Map;

public class DiskCache<T> {
    private final Map<String, File> cache;

    public DiskCache() {
        this.cache = new HashMap<>();
    }

    public void put(String key, T value) {
        try {
            File file = new File("cache/" + key + ".bin");
            ObjectOutputStream outputStream = new ObjectOutputStream(new FileOutputStream(file));
            outputStream.writeObject(value);
            outputStream.close();
            cache.put(key, file);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public T get(String key) {
        File file = cache.get(key);
        if (file != null && file.exists()) {
            try {
                ObjectInputStream inputStream = new ObjectInputStream(new FileInputStream(file));
                T value = (T) inputStream.readObject();
                inputStream.close();
                return value;
            } catch (IOException | ClassNotFoundException e) {
                e.printStackTrace();
            }
        }
        cache.remove(key);
        return null;
    }

    public static void main(String[] args) {
        DiskCache<String> cache = new DiskCache<>();
        cache.put("key1", "value1");
        String value = cache.get("key1");
        System.out.println(value);
    }
}