Question

I am writing a compiler program to read a text file. Some of the commands in the text file will tell me to skip back to a certain line in the text file and read from there. As things are, this code I have reads one line at a time until the end of the document. Is there anyway to have a parser skip back or forward to a certain line in the text file? Let us say for example I am currently on line 8 and the instruction is to go back and read line 4?

Here is my code for parsing the file.

try {
    FileInputStream fstream = new FileInputStream("compilers.txt");
    BufferedReader br = new BufferedReader(new InputStreamReader(fstream));
    String strLine;

    while ((strLine = br.readLine()) != null && checker == false) {
        // rest of code in here
    }
    in.close();
}

Answer 1

You could do this with a Map

HashMap<Integer, String>

Key is your line number and value is your line. So you can get the line by line number when you required.

Map<Integer, String> lineMap = new HashMap<Integer, String>();
int i = 1;
while ((strLine = br.readLine()) != null && !checker) {
    lineMap.put(i, strLine);
    // do what you want
    // if you are in line 8 (i=8)
    // get my line 4 (lineMap.get(4))
    i++;
}