SequenceCombineFiles.java

package ua.rumata.copyfiles;

import java.io.*;
import java.util.ArrayList;
import java.util.Vector;

public class SequenceCombineFiles {

    public static void main(String[] args) {

        String[] filesToCombine = { "someFolder/part1.txt", "someFolder/part2.txt" };
        File destFile = new File( "someFolder/combined.txt" );

        try ( FileOutputStream out = new FileOutputStream( destFile ) ) {

            ArrayList<InputStream> streams = new ArrayList<>();

            for( String fileName : filesToCombine ) {
                try ( FileInputStream stream = new FileInputStream( new File( fileName ) ) ) {
                    streams.add( stream );
                }
            }

            try ( SequenceInputStream seqIS = new SequenceInputStream( new Vector<>( streams ).elements() ) )
            {
                byte[] buffer = new byte[1024];
                int remain;

                while ((remain = seqIS.read(buffer)) > 0) {
                    out.write( buffer, 0, remain );
                }
            }

            System.out.println( "Files combined successfully" );

        } catch ( IOException e ) {
            System.out.println( e.getMessage() );
        }
    }
}