Avoided OutOfMemoryError in MD5 calculation of big files

import java.io.IOException;

import java.io.InputStream;

import java.io.UncheckedIOException;

import java.nio.ByteBuffer;

import java.nio.channels.FileChannel;

import java.nio.file.Files;

import java.nio.file.StandardOpenOption;

import java.security.MessageDigest;

import java.security.NoSuchAlgorithmException;

import java.util.Objects;

                LOG.warn("Destination file {} size mismatch with source", destinationFile.toPath().toString());

            }

            if (sourceFileInfo.getContentType() != null && 

                    !sourceFileInfo.getContentType().equals(destinationFileInfo.getContentType())) {

            if (sourceFileInfo.getContentType() != null

                    && !sourceFileInfo.getContentType().equals(destinationFileInfo.getContentType())) {

                LOG.warn("Destination file {} content type mismatch with source {} {}", destinationFile.toPath().toString(),

                        destinationFileInfo.getContentType(), sourceFileInfo.getContentType());

            }

            if (sourceFileInfo.getContentMd5() != null && 

                    !sourceFileInfo.getContentMd5().equals(md5Checksum)) {

            if (sourceFileInfo.getContentMd5() != null

                    && !sourceFileInfo.getContentMd5().equals(md5Checksum)) {

                LOG.warn("Destination file {} md5 mismatch with source {} {}", destinationFile.toPath().toString(),

                        destinationFileInfo.getContentMd5(), sourceFileInfo.getContentMd5());

            }

    private String makeMD5Checksum(File file) throws NoSuchAlgorithmException, IOException {

        MessageDigest md = MessageDigest.getInstance("MD5");

        md.update(Files.readAllBytes(file.toPath()));

        // We can't update the MessageDigest object in a single step using

        // Files.readAllBytes because we want to handle also big files and that

        // method loads all the content in memory (OutOfMemoryError has been

        // noticed for files bigger than 1GB). So multiple updates using

        // FileChannel and ByteBuffer are used

        try (FileChannel channel = FileChannel.open(file.toPath(), StandardOpenOption.READ)) {

            // creating buffer (by default it is in write mode). FileChannel will write into buffer

            ByteBuffer buffer = ByteBuffer.allocate(1024);

            int bytesRead;

            while ((bytesRead = channel.read(buffer)) != -1) {

                if (bytesRead > 0) {

                    // switch from write to read mode

                    buffer.flip();

                    md.update(buffer);

                }

                // using rewind the buffer can be filled again

                buffer.rewind();

            }

        }

        byte[] digest = md.digest();

        String checksum = DatatypeConverter.printHexBinary(digest);

        return checksum;

import org.junit.jupiter.api.BeforeAll;

import org.junit.jupiter.api.Test;

import static org.mockito.ArgumentMatchers.any;

import static org.mockito.ArgumentMatchers.anyInt;

import static org.mockito.ArgumentMatchers.eq;

import org.mockito.Mockito;

import static org.mockito.Mockito.mock;

        assertTrue(file.exists());

        assertEquals("content", Files.contentOf(file, StandardCharsets.UTF_8));

        verify(fileDao, times(1)).updateFileAttributes(anyInt(), eq("text/plain"), any(), eq(7l), eq("9A0364B9E99BB480DD25E1F0284C8555"));

        assertTrue(file.delete());

    }