有用的J2ME类--SimpleCache

下面是一个简单又快速的LRU的简单Cache类。

public class SimpleCache {
    private static long wideHits;
    private static long wideMisses;

    private Hashtable cache;
    private Vector stamps;
    private int maxSize;
    private long hits;
    private long misses;

    public static long getWideHits() {
        return wideHits;
    }

    public static long getWideMisses() {
        return wideMisses;
    }


    public SimpleCache(final int size) {
        this.maxSize = size;
        cache = new Hashtable(size);
        stamps = new Vector(size);
    }

    public int getMaxSize() {
        return maxSize;
    }

    public void setMaxSize(final int maxSize) {
        this.maxSize = maxSize;
    }

    public int getSize() {
        return cache.size();
    }

    public void add(final Object key, final Object object) {
        final Hashtable cache = this.cache;

        if (!cache.containsKey(key)) {
            if (cache.size() == maxSize) {
                discard();
            }
            cache.put(key, object);
            stamps.insertElementAt(key, 0);
        } else {
            cache.put(key, object);
            touch(key);
        }
    }

    public void remove(final Object key) {
        if (stamps.contains(key)) {
            stamps.removeElement(key);
            cache.remove(key);
        }
    }

    public void clear() {
        cache.clear();
        stamps.removeAllElements();
        hits = misses = 0;
    }

    public synchronized Object get(final Object key) {
        final Object o = cache.get(key);
        if (o != null) {
            hits++;
            wideHits++;
            touch(key);
        } else {
            misses++;
            wideMisses++;
        }
        return o;
    }

    public long getHits() {
        return hits;
    }

    public long getMisses() {
        return misses;
    }

    private void discard() {
        final Object key = stamps.lastElement();
        stamps.removeElement(key);
        cache.remove(key);
    }

    private void touch(final Object key) {
        stamps.removeElement(key);
        stamps.insertElementAt(key, 0);
    }
}