java 中对文件操作

平常经常使用JAVA对文件进行读写等操作，这里汇总一下常用的文件操作。

1、创建文件

 public static boolean createFile(String filePath){
     boolean result = false;
     File file = new File(filePath);
     if(!file.exists()){
         try {
             result = file.createNewFile();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }

     return result;
 }

2、创建文件夹

 public static boolean createDirectory(String directory){
     boolean result = false;
     File file = new File(directory);
     if(!file.exists()){
         result = file.mkdirs();
     }

     return result;
 }

3、删除文件

 public static boolean deleteFile(String filePath){
     boolean result = false;
     File file = new File(filePath);
     if(file.exists() && file.isFile()){
         result = file.delete();
     }

     return result;
 }

4、删除文件夹

递归删除文件夹下面的子文件和文件夹

 public static void deleteDirectory(String filePath){
     File file = new File(filePath);
     if(!file.exists()){
         return;
     }

     if(file.isFile()){
         file.delete();
     }else if(file.isDirectory()){
         File[] files = file.listFiles();
         for (File myfile : files) {
             deleteDirectory(filePath + "/" + myfile.getName());
         }

         file.delete();
     }
 }

5、读文件

（1）以字节为单位读取文件，常用于读二进制文件，如图片、声音、影像等文件

 public static String readFileByBytes(String filePath){
     File file = new File(filePath);
     if(!file.exists() || !file.isFile()){
         return null;
     }

     StringBuffer content = new StringBuffer();

     try {
         byte[] temp = new byte[1024];
         FileInputStream fileInputStream = new FileInputStream(file);
         while(fileInputStream.read(temp) != -1){
             content.append(new String(temp));
             temp = new byte[1024];
         }

         fileInputStream.close();
     } catch (FileNotFoundException e) {
         e.printStackTrace();
     } catch (IOException e) {
         e.printStackTrace();
     }

     return content.toString();
 }

 （2）以字符为单位读取文件，常用于读文本，数字等类型的文件，支持读取中文

 public static String readFileByChars(String filePath){
     File file = new File(filePath);
     if(!file.exists() || !file.isFile()){
         return null;
     }

     StringBuffer content = new StringBuffer();
     try {
         char[] temp = new char[1024];
         FileInputStream fileInputStream = new FileInputStream(file);
         InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream, "GBK");
         while(inputStreamReader.read(temp) != -1){
             content.append(new String(temp));
             temp = new char[1024];
         }

         fileInputStream.close();
         inputStreamReader.close();
     } catch (FileNotFoundException e) {
         e.printStackTrace();
     } catch (IOException e) {
         e.printStackTrace();
     }

     return content.toString();
 }

（3）以行为单位读取文件，常用于读面向行的格式化文件

 public static List<String> readFileByLines(String filePath){
     File file = new File(filePath);
     if(!file.exists() || !file.isFile()){
         return null;
     }

     List<String> content = new ArrayList<String>();
     try {
         FileInputStream fileInputStream = new FileInputStream(file);
         InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream, "GBK");
         BufferedReader reader = new BufferedReader(inputStreamReader);
         String lineContent = "";
         while ((lineContent = reader.readLine()) != null) {
             content.add(lineContent);
             System.out.println(lineContent);
         }

         fileInputStream.close();
         inputStreamReader.close();
         reader.close();
     } catch (FileNotFoundException e) {
         e.printStackTrace();
     } catch (IOException e) {
         e.printStackTrace();
     }

     return content;
 }

6、写文件

字符串写入文件的几个类中，FileWriter效率最高，BufferedOutputStream次之，FileOutputStream最差。

（1）通过FileOutputStream写入文件

 public static void writeFileByFileOutputStream(String filePath, String content) throws IOException{
     File file = new File(filePath);
     synchronized (file) {
         FileOutputStream fos = new FileOutputStream(filePath);
         fos.write(content.getBytes("GBK"));
         fos.close();
     }
 }

（2）通过BufferedOutputStream写入文件

 public static void writeFileByBufferedOutputStream(String filePath, String content) throws IOException{
     File file = new File(filePath);
     synchronized (file) {
         BufferedOutputStream fos = new BufferedOutputStream(new FileOutputStream(filePath));
         fos.write(content.getBytes("GBK"));
         fos.flush();
         fos.close();
     }
 }

（3）通过FileWriter将字符串写入文件

 public static void writeFileByFileWriter(String filePath, String content) throws IOException{
         File file = new File(filePath);
         synchronized (file) {
             FileWriter fw = new FileWriter(filePath);
             fw.write(content);
             fw.close();
         }
     }