java 引用之软引用与弱引用
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2024-01-30 18:22:52
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package cache;
import java.lang.ref.Reference;
import java.lang.ref.WeakReference;
import java.util.Map;
import java.util.WeakHashMap;
import java.util.concurrent.locks.ReentrantReadWriteLock;
public class WeakCache<K, V> {
private final Map<K, Reference<V>> cache = new WeakHashMap<>();
private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
public void put(K k, V v) {
lock.writeLock().lock();
try {
if (v != null) {
cache.put(k, new WeakReference(v));
} else {
cache.remove(k);
}
} finally {
lock.writeLock().unlock();
}
}
public V get(K k) {
lock.readLock().lock();
Reference<V> value = cache.get(k);
if (value == null) {
return null;
}
V v = value.get();
if (v == null) {
lock.readLock().unlock();
lock.writeLock().lock();
try {
cache.remove(k);
} finally {
lock.writeLock().unlock();
}
} else {
lock.readLock().unlock();
}
return v;
}
public void clear() {
lock.writeLock().lock();
try {
this.cache.clear();
} finally {
lock.writeLock().unlock();
}
}
}