如何在避免空指针异常的同时成功 return mp3 文件的元数据

Question

当我尝试运行获取元数据并从 mp3 文件打印它的程序时，我在项目中返回 "Exception in thread "main" java.lang.NullPointerException。mp3MetaData.main(musicdj.java:18)”。为此 class 你需要 jid3lib jar。如何避免此异常，是否需要通过底部的标签传递任何变量？

package 1234;

import java.io.File;
import java.io.IOException;

import org.farng.mp3.MP3File;
import org.farng.mp3.TagException;
import org.farng.mp3.id3.ID3v1;

public class mp3MetaData {

public static void main(String[] args) throws IOException, TagException {

    // TODO Auto-generated method stub
    File sourceFile = new     File("/Users/JohnSmith/Desktop/MusicTester/1234.mp3");
    MP3File mp3file = new MP3File(sourceFile);
    ID3v1 tag = mp3file.getID3v1Tag();
    System.out.println(tag.getAlbum());
    System.out.println(tag.getAlbumTitle());
    System.out.println(tag.getTitle()); 
    System.out.println(tag.getComment());   


}

}

任何帮助将不胜感激。

Answer 1

您的 MP3 文件可能不包含 ID3 标签。所以在使用之前检查 tag 是否是 null 。像这样：

public static void main(String[] args) throws IOException, TagException
{
    File sourceFile = new File("/Users/JohnSmith/Desktop/MusicTester/1234.mp3");
    final MP3File mp3file = new MP3File(sourceFile);
    final ID3v1 tag = mp3file.getID3v1Tag();
    if (null == tag)
    {
        System.out.println("No ID3 tag found!");
    }
    else
    {
        System.out.println(tag.getAlbum());
        System.out.println(tag.getAlbumTitle());
        System.out.println(tag.getTitle()); 
        System.out.println(tag.getComment());   
    }
}

如何在避免空指针异常的同时成功 return mp3 文件的元数据

How to successfully return the metadata off of an mp3 file while avoiding a null pointer exception

java

mp3

metadata

nullpointerexception