java之IO节点流示例，其他情况举一反三都是类似的

Posted 2021-09-08 小蜗牛爱远行

• I/O流的一般操作流程：

  • 创建或者选择数据源

  • 选择I/O流

  • 创建操作对象

  • 创建读取or存储的缓存区

  • 具体操作，写入，读取，转换等等

  • 示例：

    /*
    *文件转字节流
    */
    public static byte[] fileToByteArray(String filePath){
            //create source
            File file = new File(filePath);
            //select stream
            InputStream is = null;
            ByteArrayOutputStream os = null;
            
            try {
                //create object
                is = new FileInputStream(file);
                os = new ByteArrayOutputStream();
                //create catch place
                byte[] flush = new byte[1024*10];
                //do something
                int len = -1;
                while ((len=is.read(flush))!=-1){
                    String str = new String(flush, 0, len);
                    os.write(str.getBytes());
                }
                os.flush();
                return os.toByteArray();
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                //先开后关
                try {
                    if (null != os){
                        is.close();
                    }
                    
                } catch (IOException e) {
                    e.printStackTrace();
                }
                try {
                    if (null != is){
                        is.close();
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return null;
        }
    

    /*
    *字节流转文件
    */
    public static boolean byteArrayToFile(byte[] bytesArray, String filePath){
            //create source
            File file = new File(filePath);
            //select stream
            ByteArrayInputStream is = null;
            FileOutputStream os = null;
            try {
                //create object
                is = new ByteArrayInputStream(bytesArray);
                os = new FileOutputStream(file);
                //create catch place
                byte[] flush = new byte[1024*10];
                //do something
                int len = -1;
                while ((len=is.read(flush))!=-1){
                    os.write(flush, 0, len);
                }
                os.flush();
                return true;
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                //先开后关
                try {
                    if (null != os){
                        is.close();
                    }
    
                } catch (IOException e) {
                    e.printStackTrace();
                }
                try {
                    if (null != is){
                        is.close();
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return false;
        }
    

    public static boolean byteArrayToFile(byte[] bytesArray, String filePath){
        //create source
        File file = new File(filePath);
        //select stream(高版本JDK，无需close，try会帮你执行close, 操作字节流使用BufferedI/O，大大提高性能)
        try (ByteArrayInputStream is = new ByteArrayInputStream(bytesArray); OutputStream os = new BufferedOutputStream(new FileOutputStream(file))){
            //create catch place
            byte[] flush = new byte[1024*10];
            int len = -1;
            while ((len=is.read(flush))!=-1){
                os.write(flush, 0, len);
            }
            os.flush();
            return true;
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return false;
    }