Java: convert a file to a byte array, then convert byte array to a file.

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
 
public class Sample{
 
    public static void main(String[] args) throws FileNotFoundException, IOException {
        File file = new File("sheet1.xls");
 
        FileInputStream fis = new FileInputStream(file);

        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        byte[] buf = new byte[1024];
        try {
            for (int readNum; (readNum = fis.read(buf)) != -1;) {
                bos.write(buf, 0, readNum); 
            }
        } catch (IOException ex) {
            System.out.println(ex);
        }
        byte[] bytes = bos.toByteArray();
 
        //below is the different part
        File someFile = new File("sheet2.xls");        FileOutputStream fos = new FileOutputStream(someFile);
        fos.write(bytes);
        fos.flush();
        fos.close();
    }
}