com.qcloud.cos.internal

枚举 FileLocks

java.lang.Object

java.lang.Enum<FileLocks>

com.qcloud.cos.internal.FileLocks

所有已实现的接口:

Serializable, Comparable<FileLocks>

public enum FileLocks
extends Enum<FileLocks>

An internal utility used to provide both inter and intra JVM file locking. This works well as long as this class is loaded with the same class loader in a JVM. Otherwise, intra-JVM file locking is not guaranteed.

Per javadoc of FileLock, "File locks are held on behalf of the entire Java virtual machine. They are not suitable for controlling access to a file by multiple threads within the same virtual machine."

Hence the need for this utility class.

方法概要

方法

限定符和类型	方法和说明
static boolean	isFileLocked(File file) Returns true if the specified file is currently locked; false otherwise.
static boolean	lock(File file) Acquires an exclusive lock on the specified file, creating the file as necessary.
static boolean	unlock(File file) Unlocks a file previously locked via lock(File).
static FileLocks	valueOf(String name) 返回带有指定名称的该类型的枚举常量。
static FileLocks[]	values() 按照声明该枚举类型的常量的顺序, 返回 包含这些常量的数组。

从类继承的方法 java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

从类继承的方法 java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

方法详细资料

values

public static FileLocks[] values()

按照声明该枚举类型的常量的顺序, 返回 包含这些常量的数组。该方法可用于迭代 常量, 如下所示:

for (FileLocks c : FileLocks.values())
    System.out.println(c);

返回:

按照声明该枚举类型的常量的顺序返回的包含这些常量的数组

valueOf

public static FileLocks valueOf(String name)

返回带有指定名称的该类型的枚举常量。 字符串必须与用于声明该类型的枚举常量的 标识符完全匹配。(不允许有多余 的空格字符。)

参数:

name - 要返回的枚举常量的名称。

返回:

返回带有指定名称的枚举常量

抛出:

IllegalArgumentException - 如果该枚举类型没有带有指定名称的常量

NullPointerException - 如果参数为空值

lock

public static boolean lock(File file)

Acquires an exclusive lock on the specified file, creating the file as necessary. Caller of this method is responsible to call the unlock(File) method to prevent release leakage.

返回:

true if the locking is successful; false otherwise.

抛出:

FileLockException - if we failed to lock the file

isFileLocked

public static boolean isFileLocked(File file)

Returns true if the specified file is currently locked; false otherwise.

unlock

public static boolean unlock(File file)

Unlocks a file previously locked via lock(File).

返回:

true if the unlock is successful; false otherwise. Successful unlock means we have found and attempted to close the locking file channel, but ignoring the fact that the close operation may have actually failed.