File file=new File("demo"); ? //如果沒有寫絕對路徑的話就是相對路徑下面

if(!file.exists()){

file.mkdir();

}

File file2=new File(file,"raf.dat");

if(!file2.exists())

{

file2.createNewFile();

}

RandomAccessFile raf=new RandomAccessFile(file, "rw");

System.out.println(raf.getFilePointer());