Exception in thread "main"

Question

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Java

public static void rateSong() throws FileNotFoundException
	{
		System.out.println("Please enter the song ID: ");
		input = scan.nextInt();
		
		File songList = new File("songCollection.txt");
		
		if(songList.exists()) 
		{
			Scanner readSong= new Scanner(songList);
			
			String sid = null;
			
			while(readSong.hasNext())
			{
				String str = readSong.nextLine();
				
				sid = sid + "," + str.split(",")[0];
			}
			
			//split to return object only
			String[] songID = sid.split(",");
			
			
			for(int i=0; i<songid.length;>			{
				int id = Integer.parseInt(songID[i]);
				
				if(input==id)
				{
					System.out.println("found");
					break;
				}
				
				System.out.println("invalid input");
			}
		}
        }

I get this error when i run this code. Any idea how to solve this problem?

Exception in thread "main" java.lang.NumberFormatException: For input string: "null"
	at java.lang.NumberFormatException.forInputString(Unknown Source)
	at java.lang.Integer.parseInt(Unknown Source)
	at java.lang.Integer.parseInt(Unknown Source)
	at iTunes.Rate.rateSong(Rate.java:43)
	at iTunes.iTunesDemo.main(iTunesDemo.java:83)

Posted 23-Oct-13 5:02am

Member 10120275

Updated 23-Oct-13 5:03am

phil.o

v2

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Filipe Marques · Answer 1 · 2013-10-23T05:14:00

Hi,

You are initialize sid as null. If readSong has no next elements, sid will never be initialized. So sid.split is illigal.
Try:

Java

if(sid != null) {
    String[] songID = sid.split(",");
}

UPDATE

The error no occurs in situation above that I refered (but test sid for null).

Java

Integer.parseInt(songID[i]);

Maybe songID[i] is null. I took that error in a test. If you debug it, you will get more information.

Best regards,
Filipe Marques

Member 10351768 · Answer 2 · 2013-10-23T19:40:00

Here first initial sid with null.if once initialize the string.you can't modified that modified that one

Because String is Immutable.Thats U hot the String value as null .

Use StringBuffer in Place Of String Then It Will Work

ublic static void rateSong() throws FileNotFoundException
{
System.out.println("Please enter the song ID: ");
input = scan.nextInt();

File songList = new File("songCollection.txt");

if(songList.exists())
{
Scanner readSong= new Scanner(songList);

StringBuffer sid = null;

while(readSong.hasNext())
{
String str = readSong.nextLine();
sid = sid .append(",");
sid = sid .append( str.split(",")[0]);
}

//split to return object only
String[] songID = sid.toString().split(",");

for(int i=0; i<songid.length;> {
int id = Integer.parseInt(songID[i]);

if(input==id)
{
System.out.println("found");
break;
}

System.out.println("invalid input");
}
}
}

Exception in thread "main"

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