Reading an input text file

So i am working on a code that receives 2 strings. The string are "input#.txt" or "output#.txt" the # symbol is replaced with whatever number file is used. Now in the input file is the information I need to get to. How do I determine if that input.txt file can be opened and how do I open it.

I've tried a buffered reader and trying to just make the string a file.

import java.util.*;
import java.io.*;

public class Robot {
public static void readInstructions(String inputFileName, String outputFileName) throws InvalidRobotInstructionException{
    try{
        BufferedReader input = new BufferedReader(new FileReader(inputFileName));
        File inner = new File(inputFileName);
    Scanner in = new Scanner(input);
    PrintWriter wrt;
        wrt = new PrintWriter(outputFileName);

    if(input.readLine() == null){
        System.out.println("Input file not found.");
        return;
    }

This will read a file in:

Scanner input = new Scanner(new File("input5.txt"));

Don't forget to add throws FileNotFoundException in your main method

edit: I see you added code.