文件追加模式

           今天踩了一個坑，在分批次寫入文件時，損壞了文件，後來經過排查發現，需要使用追加模式來寫文件，否則每次都是從頭開始寫。這個就是FileInputStream的構造函數裏面的一個參數決定的。

          

/**
     * 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);

 通過append參數的描述就可以看出，這個就是決定是否是追加模式

調用時可以這樣調用.

FileOutputStream outputStream  =new FileOutputStream(new File(filePath), true);