Java 在文件中指定位置插入字符：报错

RandomAccessFile 插入写示例：

/**
 * 
 * @param skip 跳过多少过字节进行插入数据
 * @param str 要插入的字符串
 * @param fileName 文件路径
 */
public static void beiju(long skip, String str, String fileName){
	try {
		RandomAccessFile raf = new RandomAccessFile(fileName,"rw");
		if(skip <  0 || skip > raf.length()){
			System.out.println("跳过字节数无效");
			return;
		}
		byte[] b = str.getBytes();
		raf.setLength(raf.length() + b.length);
		for(long i = raf.length() - 1; i > b.length + skip - 1; i--){
			raf.seek(i - b.length);
			byte temp = raf.readByte();
			raf.seek(i);
			raf.writeByte(temp);
		}
		raf.seek(skip);
		raf.write(b);
		raf.close();
	} catch (Exception e) {
		e.printStackTrace();
	}
}

使用 velocity .

Properties p = new Properties();
        p.put(RuntimeConstants.RESOURCE_LOADER, "file");
        // filename.txt 文件所在的目錄
        p.put(RuntimeConstants.FILE_RESOURCE_LOADER_PATH, "path/to/directory");
        Velocity.init(p);

        // 文件中有個 $!{remark} 標記要被替換
        Template template = Velocity.getTemplate("filename.txt");
        // 對應 filename.txt 中的 $!{remark}
        VelocityContext context = new VelocityContext();
        context.put("remark", "Hello!");

        template.merge(context, new BufferedWriter(new OutputStreamWriter(new FileOutputStream("path/to/output.txt"), "UTF-8")));