Java 枚举类

今天在看xutils3源码的时候，在根据DaoConfig获取数据库操作类DbManagerImpl的时候，看到枚举类的应用。
1、获取调用
  public static DbManager getDb(DaoConfig daoConfig) {
return DbManagerImpl.getInstance(daoConfig);
}
2、private LruDiskCache(String dirName) {
this.cacheDb = x.getDb(DbConfigs.HTTP.getConfig());
this.cacheDir = FileUtil.getCacheDir(dirName);
if(this.cacheDir != null && (this.cacheDir.exists() || this.cacheDir.mkdirs())) {
this.available = true;
}

this.deleteNoIndexFiles();

public enum DbConfigs {
HTTP((new DaoConfig()).setDbName("xUtils_http_cache.db").setDbVersion(1).setDbOpenListener(new DbOpenListener() {
public void onDbOpened(DbManager db) {
db.getDatabase().enableWriteAheadLogging();
}
}).setDbUpgradeListener(new DbUpgradeListener() {
public void onUpgrade(DbManager db, int oldVersion, int newVersion) {
try {
db.dropDb();
} catch (DbException var5) {
LogUtil.e(var5.getMessage(), var5);
}

}
})),
COOKIE((new DaoConfig()).setDbName("xUtils_http_cookie.db").setDbVersion(1).setDbOpenListener(new DbOpenListener() {
public void onDbOpened(DbManager db) {
db.getDatabase().enableWriteAheadLogging();
}
}).setDbUpgradeListener(new DbUpgradeListener() {
public void onUpgrade(DbManager db, int oldVersion, int newVersion) {
try {
db.dropDb();
} catch (DbException var5) {
LogUtil.e(var5.getMessage(), var5);
}

}
}));

private DaoConfig config;

private DbConfigs(DaoConfig config) {
this.config = config;
}

public DaoConfig getConfig() {
return this.config;
}
}