Check out example codes for "copy file with byte java". It will help you in understanding the concepts better.

Code Example 1

var source = new File("src/resources/bugs.txt");
var dest = new File("src/resources/bugs2.txt");

Files.copy(source.toPath(), dest.toPath(), 
           StandardCopyOption.REPLACE_EXISTING);

//Source: http://zetcode.com/java/copyfile/

Code Example 2

import java.io.FileInputStream;
import java.io.FileOutputStream;

public class Main {
    public static void main(String[] args) {
        FileInputStream in =null;
        FileOutputStream out=null;
        try {
            in=new FileInputStream(args[0]);
            out=new FileOutputStream(args[1]);

            int c;
            while ((c=in.read())!=-1){
                out.write(c);
            }
        }
        catch (Exception e){
            System.out.println("Error Copping File");
        }
    }
}

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