Big Integer problems

[Roter]

Hello, Ive been trying this project for a while now, and I can't figure out a couple of things. How could you do a conditional loop with Biginteger values?
Heres my code

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.BufferedWriter;
import java.math.BigInteger;
import java.util.ArrayList;

public class Prime {

    public static void main(String[] args) { 
        //BigInteger N = BigInteger.parseLong(args[0]);
	String file = args[0];
	//reads numbers from file
 	ArrayList<BigInteger> x = read(file);

	//turns numbers into primes
	ArrayList<BigInteger> primes = turnPrimes(x);

	//writes the primes
	writePrimes(file, primes);
   }
	public static ArrayList<BigInteger> turnPrimes(ArrayList<BigInteger> originalPrimes) { 
		ArrayList<BigInteger> primes = new ArrayList<BigInteger>();
		for(int i = 0; i < originalPrimes.size(); i++) {
			primes.add(NextPrime(originalPrimes.get(i)));
		}
		return primes;
	}

	public static void writePrimes(String file, ArrayList<BigInteger> primes) {
		String fileName = file;
		if(file.contains(".txt")) {
			fileName = fileName.substring(0, file.length() - 4);
		}
		try {
			BufferedWriter writer = new BufferedWriter(new FileWriter(fileName + "primes.txt"));
			for(int i = 0;i < primes.size(); i++) {
				String number = String.valueOf(primes.get(i));
				writer.write(number);
				writer.newLine();
			}
			writer.close();
		} catch(Exception e) {
			e.printStackTrace();
		}
	}

	public static ArrayList<BigInteger> read(String file) {
		ArrayList<BigInteger> originalList = new ArrayList<BigInteger>();
		try {
			BufferedReader reader = new BufferedReader(new FileReader(file));
			while(true) {
				String line = reader.readLine();
				if(line == null) {
					break;
				}
				BigInteger longLine = BigInteger(line);
				originalList.add(longLine);
			}
		} catch(Exception e) {
			e.printStackTrace();
		}
		return originalList;
	}
			

    private static BigInteger BigInteger(String line) {	
		return null;
	}
	public static java.math.BigInteger NextPrime(BigInteger bigInteger) {
        	BigInteger N = bigInteger;
        	boolean isPrime = true;
        	if (N < 2) {
			isPrime = false;
			}
		while(N <= BigInteger.MAX_VALUE) {
			isPrime = true;
       			for (int i = 2; i*i <= N; i++) {
       			    // if i divides evenly into N, N is prime, so break out of loop
        		    if (N % i == 0) {
        		        isPrime = false;
        		    }
        		}
			if(isPrime) {
				break;
			}
			N++;
		}
	return N;
     }
}

Could you provide any advice on how to work around this? and what would be the equivalent of Long.MAXVAULE with BigInteger? Any help would be greatly appreciated

[diamonddragon]

BigInteger equivalent = BigInteger.valueOf(Long.MAX_VALUE);

[Roter]

Ok, and any ideas on how to use BigIntegers in the loops?

[Tolls]

What errors are you seeing?
Because you can't expect people to compile this for you.