| Methods Summary |
|---|
| protected V | create(K key)Called after a cache miss to compute a value for the corresponding key.
Returns the computed value or null if no value can be computed. The
default implementation returns null.
The method is called without synchronization: other threads may
access the cache while this method is executing.
If a value for {@code key} exists in the cache when this method
returns, the created value will be released with {@link #entryRemoved}
and discarded. This can occur when multiple threads request the same key
at the same time (causing multiple values to be created), or when one
thread calls {@link #put} while another is creating a value for the same
key.
return null;
|
| public final synchronized int | createCount()Returns the number of times {@link #create(Object)} returned a value.
return createCount;
|
| protected void | entryRemoved(boolean evicted, K key, V oldValue, V newValue)Called for entries that have been evicted or removed. This method is
invoked when a value is evicted to make space, removed by a call to
{@link #remove}, or replaced by a call to {@link #put}. The default
implementation does nothing.
The method is called without synchronization: other threads may
access the cache while this method is executing.
|
| public final void | evictAll()Clear the cache, calling {@link #entryRemoved} on each removed entry.
trimToSize(-1); // -1 will evict 0-sized elements
|
| public final synchronized int | evictionCount()Returns the number of values that have been evicted.
return evictionCount;
|
| public final V | get(K key)Returns the value for {@code key} if it exists in the cache or can be
created by {@code #create}. If a value was returned, it is moved to the
head of the queue. This returns null if a value is not cached and cannot
be created.
if (key == null) {
throw new NullPointerException("key == null");
}
V mapValue;
synchronized (this) {
mapValue = map.get(key);
if (mapValue != null) {
hitCount++;
return mapValue;
}
missCount++;
}
/*
* Attempt to create a value. This may take a long time, and the map
* may be different when create() returns. If a conflicting value was
* added to the map while create() was working, we leave that value in
* the map and release the created value.
*/
V createdValue = create(key);
if (createdValue == null) {
return null;
}
synchronized (this) {
createCount++;
mapValue = map.put(key, createdValue);
if (mapValue != null) {
// There was a conflict so undo that last put
map.put(key, mapValue);
} else {
size += safeSizeOf(key, createdValue);
}
}
if (mapValue != null) {
entryRemoved(false, key, createdValue, mapValue);
return mapValue;
} else {
trimToSize(maxSize);
return createdValue;
}
|
| public final synchronized int | hitCount()Returns the number of times {@link #get} returned a value that was
already present in the cache.
return hitCount;
|
| public final synchronized int | maxSize()For caches that do not override {@link #sizeOf}, this returns the maximum
number of entries in the cache. For all other caches, this returns the
maximum sum of the sizes of the entries in this cache.
return maxSize;
|
| public final synchronized int | missCount()Returns the number of times {@link #get} returned null or required a new
value to be created.
return missCount;
|
| public final V | put(K key, V value)Caches {@code value} for {@code key}. The value is moved to the head of
the queue.
if (key == null || value == null) {
throw new NullPointerException("key == null || value == null");
}
V previous;
synchronized (this) {
putCount++;
size += safeSizeOf(key, value);
previous = map.put(key, value);
if (previous != null) {
size -= safeSizeOf(key, previous);
}
}
if (previous != null) {
entryRemoved(false, key, previous, value);
}
trimToSize(maxSize);
return previous;
|
| public final synchronized int | putCount()Returns the number of times {@link #put} was called.
return putCount;
|
| public final V | remove(K key)Removes the entry for {@code key} if it exists.
if (key == null) {
throw new NullPointerException("key == null");
}
V previous;
synchronized (this) {
previous = map.remove(key);
if (previous != null) {
size -= safeSizeOf(key, previous);
}
}
if (previous != null) {
entryRemoved(false, key, previous, null);
}
return previous;
|
| public void | resize(int maxSize)Sets the size of the cache.
if (maxSize <= 0) {
throw new IllegalArgumentException("maxSize <= 0");
}
synchronized (this) {
this.maxSize = maxSize;
}
trimToSize(maxSize);
|
| private int | safeSizeOf(K key, V value)
int result = sizeOf(key, value);
if (result < 0) {
throw new IllegalStateException("Negative size: " + key + "=" + value);
}
return result;
|
| public final synchronized int | size()For caches that do not override {@link #sizeOf}, this returns the number
of entries in the cache. For all other caches, this returns the sum of
the sizes of the entries in this cache.
return size;
|
| protected int | sizeOf(K key, V value)Returns the size of the entry for {@code key} and {@code value} in
user-defined units. The default implementation returns 1 so that size
is the number of entries and max size is the maximum number of entries.
An entry's size must not change while it is in the cache.
return 1;
|
| public final synchronized java.util.Map | snapshot()Returns a copy of the current contents of the cache, ordered from least
recently accessed to most recently accessed.
return new LinkedHashMap<K, V>(map);
|
| public final synchronized java.lang.String | toString()
int accesses = hitCount + missCount;
int hitPercent = accesses != 0 ? (100 * hitCount / accesses) : 0;
return String.format("LruCache[maxSize=%d,hits=%d,misses=%d,hitRate=%d%%]",
maxSize, hitCount, missCount, hitPercent);
|
| public void | trimToSize(int maxSize)Remove the eldest entries until the total of remaining entries is at or
below the requested size.
while (true) {
K key;
V value;
synchronized (this) {
if (size < 0 || (map.isEmpty() && size != 0)) {
throw new IllegalStateException(getClass().getName()
+ ".sizeOf() is reporting inconsistent results!");
}
if (size <= maxSize || map.isEmpty()) {
break;
}
Map.Entry<K, V> toEvict = map.entrySet().iterator().next();
key = toEvict.getKey();
value = toEvict.getValue();
map.remove(key);
size -= safeSizeOf(key, value);
evictionCount++;
}
entryRemoved(true, key, value, null);
}
|
