How Can I Reset The File Pointer to the Beginning of the File in Java?

Question

I am writing a program in Java that requires me to compare the data in 2 files. I have to check each line from file 1 against each line of file 2 and if I find a match write them to a third file. After I read to the end of file 2, how do I reset the pointer to the beginning of the file?

public class FiFo {
    public static void main(String[] args) 
    {
        FileReader file1=new FileReader("d:\\testfiles\\FILE1.txt");
        FileReader file2=new FileReader("d:\\testfiles\\FILE2.txt");
        try{
            String s1,s2;
            while((s1=file1.data.readLine())!=null){
                System.out.println("s1: "+s1);
                while((s2=file2.data.readLine())!=null){
                    System.out.println("s2: "+s2);
                }
            }
            file1.closeFile();
            file2.closeFile();
        }catch (IOException e) {
            e.printStackTrace();
        }
    }
}

class FileReader {
    BufferedReader data;
    DataInputStream in;

    public FileReader(String fileName)
    {
        try{
            FileInputStream fstream = new FileInputStream(fileName);
            data = new BufferedReader(new InputStreamReader(fstream));
        }
        catch (IOException e) {
            e.printStackTrace();
        }
    } 

    public void closeFile()
    {
        try{
            in.close();
        }
        catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Answer 1

I believe RandomAccessFile is what you need. It contains: RandomAccessFile#seek and RandomAccessFile#getFilePointer.

rewind() is seek(0)

Answer 2

I think the best thing to do would be to put each line from file 1 into a HashMap; then you could check each line of file 2 for membership in your HashMap rather than reading through the entire file once for each line of file 1.

But to answer your question of how to go back to the beginning of the file, the easiest thing to do is to open another InputStream/Reader.