How to move up lines in a .txt file with BufferedReader?

Question

Making an "assembler" program for a CS course I am enrolled in. It has functions like ADD, SET, INC (increment), and JIG. Now, we are inputing a .txt file with the following layout (as example):

Keep note: A and B are just integer's that store the value throughout the program, and print out the value once it reaches the end of the text file.

INC A    (increments A by 1)
SET B 5   (set's B's value to 5)
INC B
ADD A 3  (add's 3 to A's current value)
JIG B -4 (move's backward 4 lines, so back to INC A)

So what I am confused how to do is move my BufferedReader back 4 lines? Is there a method in BufferedReader that lets you move it to a certain index/position? Otherwise, how else can I accomplish this?

Answer 1

The simplest thing to do is store the lines in an array or List.

List<String> lines = Files.readAllLines(Paths.get("myfile.txt"));

This will allow you to progress to any line at random.

To get any line you can use lines.get(n) For example you can do

int pointer = 0;
for(boolean running = true; running && pointer < lines.size(); ) {
   String line = lines.get(pointer);
   String[] parts = line.split(" +");
   switch(part[0]) {
      case "JMP":
          pointer += Integer.parseInt(parts[1]); // jump back or forth.
          continue;
      case "HALT":
          running = false;
          break;
      // other instructions
   }
   pointer++;
}