JAVA计算文件的crc32校验码

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.zip.CRC32;
import java.util.zip.CheckedInputStream;

import org.junit.Test;

public class CRCTest {

    @Test
    public void testFileCRC() {
        try {
            System.out.println(getCRC32("C:\software.xml"));
            System.out.println(checksumBufferedInputStream("C:\software.xml"));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 采用BufferedInputStream的方式加载文件
     */
    public static long checksumBufferedInputStream(String filepath) throws IOException {
        InputStream inputStream = new BufferedInputStream(new FileInputStream(filepath));
        CRC32 crc = new CRC32();
        byte[] bytes = new byte[1024];
        int cnt;
        while ((cnt = inputStream.read(bytes)) != -1) {
            crc.update(bytes, 0, cnt);
        }
        inputStream.close();
        return crc.getValue();
    }

    /**
     * 使用CheckedInputStream计算CRC
     */
    public static Long getCRC32(String filepath) throws IOException {
        CRC32 crc32 = new CRC32();
        FileInputStream fileinputstream = new FileInputStream(new File(filepath));
        CheckedInputStream checkedinputstream = new CheckedInputStream(fileinputstream, crc32);
        while (checkedinputstream.read() != -1) {
        }
        checkedinputstream.close();
        return crc32.getValue();
    }
}

注意如果要获取CRC32的getValues返回值的字符串，应该采用：  Long.toHexString(crc32.getValue())    方式返回字符串。

原因如下：