I need help in how to call a file in java: (file names are sample_input1.txt, sample_input2.txt, sample_input3.txt)

//These are all the imports you are allowed, don't add any more!
import java. util. Scanner;
import java. io. File;
import java. io. IOException;

class SimpleCompiler {

public static Node fileToQueue(String filename) throws IOException {
//given a file name, open that file in a scanner and create a queue of nodes
//the head of the queue of nodes should be the start of the queue
//the values in the nodes should be the strings read in each time you call
//next() on the scanner
return null;
}

public Node compile(Node input, int numSymbols) {
//Given an input queue of symbols, process the number of symbols
//specified (numSymbols) and update the callStack and symbols
//variables appropriately to reflect the state of the "SimpleCompiler"
//(see below the "do not edit" line for these variables).

//Return the remaining queue items.

//For example, if input is the head of a linked list 3 -> 2 -> +
//and numSymbols=2, you would push 3 and push 2, then return the linked
//list with just the + node remaining.

return null;
}

public static void testThisCode() {
//edit this as much as you want, if you use main without any arguments,
//this is the method that will be run instead of the program
System. out. println("You need to put test code in testThisCode() to run SimpleCompiler with no parameters.");
}

//DON'T EDIT BELOW THIS LINE
//EXCEPT TO ADD JAVADOCS

//don't edit these...
public static final String[] INT_OPS = {"+","-","*","/"};
public static final String[] ASSIGN_OPS = {"=","+=","-=","*=","/="};

//or these...
public CallStack callStack = new CallStack<>();
public LookUpBST symbols = new LookUpBST<>();

public static void main(String[] args) {
//this is not a testing main method, so don't edit this
//edit testThisCode() instead!

if(args. length == 0) {
testThisCode();
return;
}

if(args. length != 2 || !(args[1].equals("false") || args[1].equals("true"))) {
System. out. println("Usage: java SimpleCompiler [filename] [true|false]");
System. exit(0);
}

try {
(new SimpleCompiler()).runCompiler(args[ 0], args[1].equals("true"));
}
catch(IOException e) {
System. out. println(e. toString());
e. printStackTrace();
}
}

//provided, don't change this
public void runCompiler(String filename, boolean debug) throws IOException {
Node input = fileToQueue(filename);
System. out. println("\nProgram: " + Node. listToString(input));

if(!debug) {
while(input != null) {
input = compile(input, 10);
}
}
else {
Scanner s = new Scanner(System. in);
for(int i = 1; input != null; i++) {
System. out. println("\n Step " + i + " \n");
System. out. println("Step Output");
input = compile(input, 1);
System. out. println("Lookup BST");
System. out. println(symbols);
System. out. println("Call Stack");
System. out. println(callStack);
if(input != null) {
System. out. println("Program Remaining");
System. out. println(Node. listToString(input));
}
System. out. println("\nPress Enter to Continue");
s. nextLine();
}
}
}
}