今天踩了一个坑,在分批次写入文件时,损坏了文件,后来经过排查发现,需要使用追加模式来写文件,否则每次都是从头开始写。这个就是FileInputStream的构造函数里面的一个参数决定的。
/**
* Creates a file output stream to write to the file represented by
* the specified <code>File</code> object. If the second argument is
* <code>true</code>, then bytes will be written to the end of the file
* rather than the beginning. A new <code>FileDescriptor</code> object is
* created to represent this file connection.
* <p>
* First, if there is a security manager, its <code>checkWrite</code>
* method is called with the path represented by the <code>file</code>
* argument as its argument.
* <p>
* If the file exists but is a directory rather than a regular file, does
* not exist but cannot be created, or cannot be opened for any other
* reason then a <code>FileNotFoundException</code> is thrown.
*
* @param file the file to be opened for writing.
* @param append if <code>true</code>, then bytes will be written
* to the end of the file rather than the beginning
* @exception FileNotFoundException if the file exists but is a directory
* rather than a regular file, does not exist but cannot
* be created, or cannot be opened for any other reason
* @exception SecurityException if a security manager exists and its
* <code>checkWrite</code> method denies write access
* to the file.
* @see java.io.File#getPath()
* @see java.lang.SecurityException
* @see java.lang.SecurityManager#checkWrite(java.lang.String)
* @since 1.4
*/
public FileOutputStream(File file, boolean append);
通过append参数的描述就可以看出,这个就是决定是否是追加模式
调用时可以这样调用.
FileOutputStream outputStream =new FileOutputStream(new File(filePath), true);