Java 100例：ZIP 壓縮與解壓縮 (ZipInputStream/ZipOutputStream)

使用 java.util.zip 套件實作多檔案壓縮為 ZIP、解壓縮輸出至標準輸出、列出壓縮檔清單。採用 CheckedInputStream/OutputStream 搭配 Adler32 校驗和。

import java.io.*;
import java.util.*;
import java.util.zip.*;

public class ZipDemo {
    // 壓縮：參數陣列 args[0] 為輸出 zip 檔名，args[1..] 為欲壓縮檔案
    public void zipFiles(String[] args) {
        try (FileOutputStream fos = new FileOutputStream(args[0] + ".zip");
             CheckedOutputStream cos = new CheckedOutputStream(fos, new Adler32());
             ZipOutputStream zos = new ZipOutputStream(new BufferedOutputStream(cos))) {
            zos.setComment("Java Zip Test");
            for (int i = 1; i < args.length; i++) {
                System.out.println("Adding: " + args[i]);
                try (BufferedReader br = new BufferedReader(new FileReader(args[i]))) {
                    zos.putNextEntry(new ZipEntry(args[i]));
                    int c;
                    while ((c = br.read()) != -1) zos.write(c);
                }
            }
            System.out.println("Checksum: " + cos.getChecksum().getValue());
        } catch (Exception e) { e.printStackTrace(); }
    }

    // 解壓縮：輸出至 System.out (示範用)
    public void unzip(String zipFile) {
        try (FileInputStream fis = new FileInputStream(zipFile + ".zip");
             CheckedInputStream cis = new CheckedInputStream(fis, new Adler32());
             ZipInputStream zis = new ZipInputStream(new BufferedInputStream(cis))) {
            System.out.println("Checksum: " + cis.getChecksum().getValue());
            ZipEntry entry;
            while ((entry = zis.getNextEntry()) != null) {
                System.out.println("Extracting: " + entry.getName());
                int b;
                while ((b = zis.read()) != -1) System.out.write(b);
            }
        } catch (Exception e) { e.printStackTrace(); }
    }

    // 列出壓縮檔內容
    public void list(String zipFile) {
        try (ZipFile zf = new ZipFile(zipFile + ".zip")) {
            Enumeration en = zf.entries();
            while (en.hasMoreElements()) System.out.println(en.nextElement());
        } catch (Exception e) { e.printStackTrace(); }
    }

    public static void main(String[] args) {
        if (args.length == 0) return;
        ZipDemo demo = new ZipDemo();
        demo.zipFiles(args);
        demo.unzip(args[0]);
        demo.list(args[0]);
    }
}

改進建議：

• 實務解壓縮應寫入檔案而非標準輸出，使用 Files.copy(zis, targetPath) (Java 8+)。
• 大檔案建議使用 ZipFile 隨機存取而非串流 ZipInputStream。
• 中文檔名編碼問題：Java 7+ 可指定 ZipFile(..., StandardCharsets.UTF_8)。