通过java.util.zip.ZipFile解析zip文件，遍历Entry生成新的Zip文件，新旧两个文件的MD5值不一样

修改zip文件，删除ZipEntry，再还原ZipEntry后，想保持MD5值一样，可以采取直接修改Zip文件内容的方式。

zip文件格式参考

https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT

import java.io.*;
import java.security.NoSuchAlgorithmException;
import java.util.Enumeration;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;
import java.util.zip.ZipOutputStream;

public class ZipCopyDemo {

    public static void main(String[] args) throws IOException {

        File src = new File("d:/tmp/junit-4.12.jar");
        File dest = new File("d:/tmp/junit-4.12-2.jar");

        ZipFile zipSrc = new ZipFile(src);
        ZipOutputStream zos = new ZipOutputStream(new FileOutputStream(dest));

        Enumeration srcEntries = zipSrc.entries();
        while (srcEntries.hasMoreElements()) {
            ZipEntry srcentry = (ZipEntry) srcEntries.nextElement();
            ZipEntry destEntry = new ZipEntry(srcentry);
            zos.putNextEntry(destEntry);
            org.apache.commons.io.IOUtils.copy(zipSrc.getInputStream(srcentry), zos);
            zos.closeEntry();
        }

        zos.finish();
        zos.close();
        zipSrc.close();

        System.out.println(src.getAbsolutePath() + "\t md5=" + getMD5(readcontent(src)));
        System.out.println(dest.getAbsolutePath() + "\t md5=" + getMD5(readcontent(dest)));

    }

    private static byte[] readcontent(File file) throws IOException {
        try (InputStream in = new FileInputStream(file);) {
            return toByteArray(in, (int) file.length());
        }
    }

    public static byte[] toByteArray(InputStream input, int size) throws IOException {

        if (size == 0) {
            return new byte[0];
        }

        byte[] data = new byte[size];
        int offset = 0;
        int readed;

        while (offset < size && (readed = input.read(data, offset, size - offset)) != -1) {
            offset += readed;
        }

        if (offset != size) {
            throw new IOException("Unexpected readed size. current: " + offset + ", excepted: " + size);
        }

        return data;
    }

    public static String getMD5(byte[] source) {

        String s = null;

        char hexDigits[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
                'a', 'b', 'c', 'd', 'e', 'f'};
        try {

            java.security.MessageDigest md = java.security.MessageDigest
                    .getInstance("MD5");
            md.update(source);

            byte tmp[] = md.digest();

            char str[] = new char[16 * 2];

            int k = 0;
            for (int i = 0; i < 16; i++) {
                byte byte0 = tmp[i];
                str[k++] = hexDigits[byte0 >>> 4 & 0xf];
                str[k++] = hexDigits[byte0 & 0xf];
            }
            s = new String(str);

        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException(e);
        }

        return s;
    }

}