java读取文件

public static void readFileByBytes(String fileName) {
        File file = new File(fileName);
        InputStream in = null;
        StringBuffer sb=new StringBuffer();
        try {

            if(file.isFile() && file.exists()){ //判断文件是否存在
                System.out.println("以字节为单位读取文件内容，一次读多个字节：");
                // 一次读多个字节
                byte[] tempbytes = new byte[1024];
                int byteread = 0;
                in = new FileInputStream(file);
                ReadFromFile.showAvailableBytes(in);
                // 读入多个字节到字节数组中，byteread为一次读入的字节数
                while ((byteread = in.read(tempbytes)) != -1) {
                  //  System.out.write(tempbytes, 0, byteread);
                    String str=new String(tempbytes,0,byteread);
                    sb.append(str);
                }
            }else{
                System.out.println("找不到指定的文件,请确认文件路径是否正确");
            }


            String data = sb.toString() ;

          } catch (Exception e) {
            System.out.println("读取文件内容出错");
            e.printStackTrace();
        } finally {
            if (in != null) {
                try {
                    in.close();
                } catch (IOException e1) {
                }
            }
        }
}
   

/**
 * 显示输入流中的字节数
 */
private static void showAvailableBytes(InputStream in) {
    try {
        System.out.println("当前字节输入流中的字节数为:" + in.available());
    } catch (IOException e) {
        e.printStackTrace();
    }
}

public static void main(String[] args) {

    // String fileName = "D:/file/test3.json";
    String fileName = "D:/file/1.json";
    readFileByBytes(fileName);


}