package java.nio.file;
/**
* Defines the standard open options.
*
* @since 1.7
*/
public enum StandardOpenOption implements OpenOption {
/**
* Open for read access.
* 讀取一個已存在的文件,如果文件不存在或被佔用則拋出異常
*/
READ,
/**
* Open for write access.
* 以追加到文件頭部的方式,寫入一個已存在的文件,如果文件不存在或被佔用則拋出異常
*/
WRITE,
/**
* If the file is opened for {@link #WRITE} access then bytes will be written
* to the end of the file rather than the beginning.
*
* <p> If the file is opened for write access by other programs, then it
* is file system specific if writing to the end of the file is atomic.
* 以追加到文件尾部的方式,寫入一個已存在的文件,如果文件不存在或被佔用則拋出異常
*/
APPEND,
/**
* If the file already exists and it is opened for {@link #WRITE}
* access, then its length is truncated to 0. This option is ignored
* if the file is opened only for {@link #READ} access.
*/
TRUNCATE_EXISTING,
/**
* Create a new file if it does not exist.
* This option is ignored if the {@link #CREATE_NEW} option is also set.
* The check for the existence of the file and the creation of the file
* if it does not exist is atomic with respect to other file system
* operations.
* 創建一個空文件,如果文件存在則不創建
*/
CREATE,
/**
* Create a new file, failing if the file already exists.
* The check for the existence of the file and the creation of the file
* if it does not exist is atomic with respect to other file system
* operations.
* 創建一個空文件,如果文件存在則報錯
*/
CREATE_NEW,
/**
* Delete on close. When this option is present then the implementation
* makes a <em>best effort</em> attempt to delete the file when closed
* by the appropriate {@code close} method. If the {@code close} method is
* not invoked then a <em>best effort</em> attempt is made to delete the
* file when the Java virtual machine terminates (either normally, as
* defined by the Java Language Specification, or where possible, abnormally).
* This option is primarily intended for use with <em>work files</em> that
* are used solely by a single instance of the Java virtual machine. This
* option is not recommended for use when opening files that are open
* concurrently by other entities. Many of the details as to when and how
* the file is deleted are implementation specific and therefore not
* specified. In particular, an implementation may be unable to guarantee
* that it deletes the expected file when replaced by an attacker while the
* file is open. Consequently, security sensitive applications should take
* care when using this option.
*
* <p> For security reasons, this option may imply the {@link
* LinkOption#NOFOLLOW_LINKS} option. In other words, if the option is present
* when opening an existing file that is a symbolic link then it may fail
* (by throwing {@link java.io.IOException}).
* 流和管道關閉時刪除文件,如果流和管道沒有關閉,則在Java虛擬機退出時刪除文件
*/
DELETE_ON_CLOSE,
/**
* Sparse file. When used with the {@link #CREATE_NEW} option then this
* option provides a <em>hint</em> that the new file will be sparse. The
* option is ignored when the file system does not support the creation of
* sparse files.
*/
SPARSE,
/**
* Requires that every update to the file's content or metadata be written
* synchronously to the underlying storage device.
*
* @see <a href="package-summary.html#integrity">Synchronized I/O file integrity</a>
*/
SYNC,
/**
* Requires that every update to the file's content be written
* synchronously to the underlying storage device.
*
* @see <a href="package-summary.html#integrity">Synchronized I/O file integrity</a>
*/
DSYNC;
}
StandardOpenOption詳解
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