Java: Simple Text Sorter

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class Main {

    public static void main(String[] args) throws IOException {
        System.out.println("INPUT FILEPATH: ");

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String filepath;
        try {filepath = br.readLine();}
        catch (IOException ex) {filepath = "";}

        File file = new File(filepath);
        if (!file.exists()) {System.out.println("INVALID FILEPATH"); return;}
        if (!file.getName().endsWith(".txt")) {System.out.println("FILE MUST BE A TEXT FILE"); return;}

        BufferedReader fileread = new BufferedReader(new FileReader(file));

        List<String> lines = new ArrayList<String>();
        String line = new String();

        while (line != null) {
            line = fileread.readLine();
            if (line!=null) lines.add(line);
        } fileread.close();

        System.out.println(lines.size());

        Collections.sort(lines);

        BufferedWriter bw = new BufferedWriter(new FileWriter(file));
        for (String write : lines) {
            bw.write(write);
            bw.newLine();
        } bw.close();

    }
}