使用Apache bzip2库的NullPointerException

Question

我正在使用Apache Ant的BZip2压缩库.文档见 - http://javadoc.haefelinger.it/org.apache.ant/1.7.1/org/apache/tools/bzip2/CBZip2InputStream.html

我运行代码时不断收到此错误 -

   Exception in thread "main" java.lang.NullPointerException
    at org.apache.tools.bzip2.CBZip2InputStream.bsR(CBZip2InputStream.java:323)
    at org.apache.tools.bzip2.CBZip2InputStream.bsGetUChar(CBZip2InputStream.java:341)
    at org.apache.tools.bzip2.CBZip2InputStream.initBlock(CBZip2InputStream.java:230)
    at org.apache.tools.bzip2.CBZip2InputStream.<init>(CBZip2InputStream.java:178)
    at org.apache.tools.bzip2.bzipCompression.main(bzipCompression.java:37)

错误在线 -

**CBZip2InputStream cin = new CBZip2InputStream(fileInputStream);**

我的源代码是 -

  public static void main(String[] args) throws IOException, NullPointerException {
    // TODO Auto-generated method stub

    FileReader inFile = new FileReader("alice29.txt");
    BufferedReader buff = new BufferedReader(inFile);

    FileOutputStream fout = new FileOutputStream("alicea.txt");
    fout.write("BZ".getBytes());


    CBZip2OutputStream czout = new CBZip2OutputStream (fout);

    String message = buff.readLine(); // read first line

    while(message!=null){
        byte[] input = message.getBytes();
        czout.write(input);
        message = buff.readLine();
    }
    czout.flush();
    czout.close();


    InputStream fileInputStream = new FileInputStream("alicea.txt");
    CBZip2InputStream cin = new CBZip2InputStream(fileInputStream);
    FileOutputStream decOut = new FileOutputStream("decompressedAlice.txt");


    byte[] buf = new byte[100000];
    int len;

    while((len = cin.read(buf))>0){
        decOut.write(buf, 0, len);
    }
    decOut.close();
    cin.close();

}

非常感谢你的帮助.

Answer 1

您正在打开alicea.txt的FileOutputStream

FileOutputStream fout = new FileOutputStream("alicea.txt");

此OutputStream永远不会在您的代码中关闭,但在错误行中,您在同一文件上打开FileInputStream:

InputStream fileInputStream = new FileInputStream("alicea.txt");
CBZip2InputStream cin = new CBZip2InputStream(fileInputStream);

恕我直言,当您在文件上打开FileOutputStream时,无法在同一文件上打开文件InputStream.这可能是为什么你的FileInputStream为NULL并抛出异常的原因.

更新: CBZip2InputStream中存在已知错误以及2002年描述的解决方案(仍可在MarkMail中找到),该解决方案仍然存在.您必须下载java-classes,并且可能不使用ready build .jar存档.在CBZip2InputStream.java的initialize()方法中更改以下行:

原始代码(从第213行开始):

private void initialize() {
    char magic3, magic4;
    magic3 = bsGetUChar();
    magic4 = bsGetUChar();
    if (magic3 != 'h' || magic4 < '1' || magic4 > '9') {
        bsFinishedWithStream();
        streamEnd = true;
        return;
    }
    setDecompressStructureSizes(magic4 - '0');
    computedCombinedCRC = 0;
}

将其更改为:

private void initialize() {
    char magic1, magic2; 
    char magic3, magic4; 
    magic1 = bsGetUChar(); 
    magic2 = bsGetUChar(); 
    magic3 = bsGetUChar(); 
    magic4 = bsGetUChar(); 
    if (magic1 != 'B' || magic2 != 'Z' | magic3 != 'h' || magic4 < '1' || magic4 > '9') {   
        bsFinishedWithStream();
        streamEnd = true;
        return;
    }
    setDecompressStructureSizes(magic4 - '0');
    computedCombinedCRC = 0;
}

最后更新: 我刚刚审阅了apache ant的svn; 主干中的错误是固定的.但尽管如此,仍有许多下载仍包含此错误.我还意外地下载了一个旧版本来测试你的问题.