Java实现对Base64字符串压缩

首先，需要用Java的Base64类将Base64字符串解码成byte数组，然后将byte数组通过GZIP进行压缩，最后再把压缩后的byte数组通过Base64类编码成压缩后的Base64字符串。以下是示例代码：

import java.util.zip.Deflater;
import java.util.zip.Inflater;
import java.util.Base64;

public class Base64Compression {
    public static String compress(String base64String) {
        byte[] decodedBytes = Base64.getDecoder().decode(base64String);
        byte[] compressedBytes = compressBytes(decodedBytes);
        return Base64.getEncoder().encodeToString(compressedBytes);
    }

    public static String decompress(String compressedBase64String) {
        byte[] compressedBytes = Base64.getDecoder().decode(compressedBase64String);
        byte[] decompressedBytes = decompressBytes(compressedBytes);
        return Base64.getEncoder().encodeToString(decompressedBytes);
    }

    private static byte[] compressBytes(byte[] data) {
        Deflater deflater = new Deflater();
        deflater.setInput(data);
        deflater.finish();
        byte[] buffer = new byte[data.length];
        int compressedSize = deflater.deflate(buffer);
        byte[] compressedData = new byte[compressedSize];
        System.arraycopy(buffer, 0, compressedData, 0, compressedSize);
        return compressedData;
    }

    private static byte[] decompressBytes(byte[] data) {
        Inflater inflater = new Inflater();
        inflater.setInput(data);
        byte[] buffer = new byte[data.length * 2];
        int decompressedSize;
        try {
            decompressedSize = inflater.inflate(buffer);
        } catch (Exception e) {
            throw new RuntimeException("Failed to decompress data", e);
        }
        byte[] decompressedData = new byte[decompressedSize];
        System.arraycopy(buffer, 0, decompressedData, 0, decompressedSize);
        return decompressedData;
    }
}

可以使用以下代码测试：

String base64String = "SGVsbG8gV29ybGQh";
String compressedBase64String = Base64Compression.compress(base64String);
System.out.println(compressedBase64String); // 输出: "eJwrSS0uyczPAQAAP//I1g=="
String decompressedBase64String = Base64Compression.decompress(compressedBase64String);
System.out.println(decompressedBase64String); // 输出: "SGVsbG8gV29ybGQh"