java文件读取与保存

文件读取与保存

		Long startTime=System.currentTimeMillis();
		String jsonStr = "";
		try {
			File jsonFile = new File("E:\\json\\"+ "json" + ".json");
			FileReader fileReader = new FileReader(jsonFile);
			Reader reader = new InputStreamReader(new FileInputStream(jsonFile),"utf-8");
			StringBuffer sb = new StringBuffer();
//			int ch = 0;
//			while ((ch = reader.read()) != -1) {
//				sb.append((char) ch);
//			}
			BufferedReader buf = new BufferedReader(reader);
			String line=null;
			while((line = buf.readLine())!=null) //此过程中，读入缓冲区一行一行的读取数据，效率高
			{
				sb.append(line);
			}
			fileReader.close();
			reader.close();
			jsonStr = sb.toString();
			Long endTime = System.currentTimeMillis();
			System.out.println("程序运行时间：" + (endTime - startTime) + "ms");
		} catch (IOException e) {
			e.printStackTrace();
		}

List<FbAttachment> fbAttachmentList=fbAttachmentService.getFbList();
		String json= JSON.toJSONString(fbAttachmentList);
		BufferedWriter writer = null;
		File file = new File("E:\\json\\"+ "json" + ".json");
		//如果文件不存在，则新建一个
		if(!file.exists()){
			try {
				file.createNewFile();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		//写入
		try {
			writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file,true), "UTF-8"));
			writer.write(json);
		} catch (IOException e) {
			e.printStackTrace();
		}finally {
			try {
				if(writer != null){
					writer.close();
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		System.out.println("文件写入成功！");
	}