这个方法会从LinkedHashMap中移除指定key对应的value并返回这个value，我们可以看到它的内部还调用了entryRemoved方法，如果有需要的话，我们可以重写entryRemoved方法来做一些资源回收的工作。
2. DiskLruCache的使用
（1）初始化DiskLruCache
通过查看DiskLruCache的源码我们可以发现，DiskLruCache就存在如下一个私有构造方法：
private DiskLruCache(File directory, int appVersion, int valueCount, long maxSize) {
this.directory = directory;
this.appVersion = appVersion;
this.journalFile = new File(directory, JOURNAL_FILE);
this.journalFileTmp = new File(directory, JOURNAL_FILE_TMP);
this.valueCount = valueCount;
this.maxSize = maxSize;
}
因此我们不能直接调用构造方法来创建DiskLruCache的实例。实际上DiskLruCache为我们提供了open静态方法来创建一个DiskLruCache实例，我们来看一下这个方法的实现：
public static DiskLruCache open(File directory, int appVersion, int valueCount, long maxSize)
throws IOException {
if (maxSize <= 0) {
throw new IllegalArgumentException("maxSize <= 0");
}
if (valueCount <= 0) {
throw new IllegalArgumentException("valueCount <= 0");
}
// prefer to pick up where we left off
DiskLruCache cache = new DiskLruCache(directory, appVersion, valueCount, maxSize);
if (cache.journalFile.exists()) {
try {
cache.readJournal();
cache.processJournal();
cache.journalWriter = new BufferedWriter(new FileWriter(cache.journalFile, true),
IO_BUFFER_SIZE);
return cache;
} catch (IOException journalIsCorrupt) {
// System.logW("DiskLruCache " + directory + " is corrupt: "
// + journalIsCorrupt.getMessage() + ", removing");
cache.delete();
}
}
// create a new empty cache
directory.mkdirs();
cache = new DiskLruCache(directory, appVersion, valueCount, maxSize);
cache.rebuildJournal();
return cache;
}
