IdeaProjects/Test/src/com/renchao/ZipDemo.java

package com.renchao;

import org.junit.Test;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.StandardOpenOption;
import java.util.List;
import java.util.zip.CRC32;
import java.util.zip.CheckedInputStream;
import java.util.zip.Deflater;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;

public class ZipDemo {
    public static void main(String[] args) throws Exception {
        // 创建一个ZipOutputStream类的对象
        ZipOutputStream out = new ZipOutputStream(new FileOutputStream("C:\\Users\\RENCHAO\\Desktop\\新建文件夹\\output.zip"));
        // 创建一个File对象，表示要压缩的文件夹
        File file = new File("C:\\Users\\RENCHAO\\Desktop\\aa");
        // 调用compress方法，将file对象压缩到out对象中
        compress(out, file, "");
        // 关闭out对象
        out.close();
    }

    public static void compress(ZipOutputStream out, File file, String base) throws Exception {
        if (file.isDirectory()) {
            // 如果file对象是一个目录，则获取该目录下的所有文件和目录
            File[] files = file.listFiles();
            // 如果files数组不为空，则遍历files数组中的所有元素
            if (files != null && files.length > 0) {
                for (File f : files) {
                    // 递归调用compress方法，将f对象压缩到out对象中
                    compress(out, f, base + file.getName() + "/");
                }
            }
        } else {
            // 如果file对象是一个文件，则创建一个ZipEntry对象，表示该文件在压缩包中的路径和名称
            ZipEntry entry = new ZipEntry(base + file.getName());
            // 将entry对象添加到out对象中
            out.putNextEntry(entry);
            // 创建一个FileInputStream类的对象
            FileInputStream in = new FileInputStream(file);
            // 创建一个byte数组
            byte[] buffer = new byte[1024];
            int len;
            // 读取in对象中的数据到buffer数组中，直到读取完毕
            while ((len = in.read(buffer)) > 0) {
                // 将buffer数组中的数据写入到out对象中
                out.write(buffer, 0, len);
            }
            // 关闭in对象
            in.close();
        }
    }



    @Test
    public void test01() throws IOException {
        // ArrayList<File> list = new ArrayList<>();
        // collect(new File("C:\\Users\\RENCHAO\\Desktop\\temp-sss\\aa\\20240314094355A076"), list);

        long l = System.currentTimeMillis();
        File file = new File("C:\\Users\\RENCHAO\\Desktop\\aa.pdf");

        try (/*FileInputStream in = new FileInputStream(file);*/
             ZipOutputStream out = new ZipOutputStream(new FileOutputStream("C:\\Users\\RENCHAO\\Desktop\\temp-sss\\aa\\output.zip"))) {
            ZipEntry entry = new ZipEntry("aa.pdf");
            entry.setMethod(ZipEntry.STORED);

            // Set the size of the file
            entry.setSize(file.length());


            // Set the CRC-32 checksum of the file
            entry.setCrc(calcChecksum(file));



            out.setLevel(Deflater.NO_COMPRESSION);
            out.putNextEntry(entry);
            System.out.println("创建entry:" + (System.currentTimeMillis() - l));

            l = System.currentTimeMillis();
            // byte[] buffer = new byte[2048];
            // int len;
            // while ((len = in.read(buffer)) > 0) {
            //     out.write(buffer, 0, len);
            // }

            try (FileChannel fileChannel = FileChannel.open(file.toPath(), StandardOpenOption.READ)) {
                ByteBuffer buffer = ByteBuffer.allocate(8192); // 8KB缓冲区
                int bytesRead;
                while ((bytesRead = fileChannel.read(buffer)) != -1) {
                    buffer.flip(); // 切换到读模式
                    out.write(buffer.array(), 0, bytesRead);
                    buffer.clear(); // 清空缓冲区
                }
            }

            //ZipOutputStream.write可以使用NIO操作吗，以提高效率

            System.out.println("压缩完成:" + (System.currentTimeMillis() - l));
        }


    }

    public void collect(File file, List<File> list) {
        if (file.isDirectory()) {
            File[] files = file.listFiles();
            if (files != null && files.length > 0) {
                for (File f : files) {
                    collect(f, list);
                }
            }
        } else {
            list.add(file);
        }
    }


    // Calculate CRC-32 checksum of a file
    private static long calcChecksum(File file) throws IOException {
        try (FileInputStream fis = new FileInputStream(file);
             CheckedInputStream cis = new CheckedInputStream(fis, new CRC32())) {
            byte[] buffer = new byte[2048];
            while (cis.read(buffer) >= 0) {
                // Reading the file to calculate CRC-32 checksum
            }
            return cis.getChecksum().getValue();
        }
    }

    private static long calcChecksum2(File file) throws IOException {
        try (FileChannel fileChannel = FileChannel.open(file.toPath(), StandardOpenOption.READ)) {
            ByteBuffer buffer = ByteBuffer.allocate(1024);
            CRC32 crc32 = new CRC32();
            while (fileChannel.read(buffer) != -1) {
                buffer.flip();
                crc32.update(buffer);
                buffer.clear();
            }
            return crc32.getValue();
        }
    }
}