从文件读取直到特定的字符序列

Question

i have a JSON file which looks like this:

{  
   "id":25,
   "type":0,
   "date":"Aug 28, 2017 12:14:28 PM",
   "isOpen":true,
   "message":"test"
}
/* 
some lines here, comment, not json
*/

what I would like to do is to be able to read from the file until it detects the beginning of the comment section "/*".

I was able to write a bit of code, but the output doesn't seem to be ok for some reasons:

BufferedReader br = null;
FileReader fr = null;
String comm = "/*";
fr=new FileReader(FILENAME);
br=new BufferedReader(fr);

String currentLine;

while((currentLine=br.readLine())!=null&&!(currentLine=br.readLine()).equals(comm))
{
    System.out.println(sCurrentLine);
}
br.close();

The output only gives me this:

"id": 25,
"date": "Aug 28, 2017 12:14:28 PM",

I dont have the beginning of the json section { nor the whole json message "isOpen" , "message" ...

How can i do to read and store the result in a string until the comment section ?

Answer 1

You are calling twice currentLine = br.readLine() , therefore reading two lines. It's the same problem people have when they use

Scanner sc = new Scanner(System.in);
if (sc.nextLine() != null) // This reads a line
    myString = sc.nextLine(); //This reads the next line!

You shouldn't call it the second time -- directly compare your currentLine with com .

Try:

String comm = "/*";
BufferedReader br = new BufferedReader(new FileReader(FILENAME););

StringBuilder sb = new StringBuilder();
String currentLine;

while ((currentLine = br.readLine()) != null && !(currentLine.equals(comm)) {
    //System.out.println(currentLine);
    sb.append(currentLine);
    sb.append("\n");
}
br.close();
System.out.println(sb.toString());

If you want to use a Scanner , it would be something like:

StringBuilder sb = new StringBuilder();
Scanner sc = new Scanner(FILENAME);

while (sc.hasNext())
    sb.append(sc.next());
System.out.println(sb.toString());