java outer while loop is not iterating

Question

I wrote the following code and the inner for loop works fine, but the outer loop does not iterate. Here is my code:

BufferedReader userfeatures = new BufferedReader(new FileReader("userFeatureVectorsTest.csv"));
BufferedReader itemfeatures = new BufferedReader(new FileReader("ItemFeatureVectorsTest.csv"));         

while ((Uline = userfeatures.readLine()) != null) 
{
    for (String Iline = itemfeatures.readLine(); Iline != null; Iline = itemfeatures.readLine()) 
    {           
         System.out.println(intersect(Uline, Iline).size()); 
         System.out.println(union(Uline, Iline).size());  
    }
}
userfeatures.close();
itemfeatures.close();

}

It finds the intersection and union of the first line of the first file with every line of the 2nd file and then it stops. However, I need to continue and repeat the same procedure for next lines of the first file. So, I think there is some problems related to my outer while loop, but I could not find what is the proble :| Could someone help me please? Thanks

i´d rather say that it is looping over and over and your for loop isn´t looping anymore since you already read thorugh itemfeatures and itemfeatures.readLine() returns null since you are already at the end of the file. — SomeJavaGuy
– SomeJavaGuy, Commented Dec 8, 2015 at 16:07
You could put the initialisation of itemFeatures inside the outer loop. Or you could read the contents of the second file once and cache the information you need. — khelwood
– khelwood, Commented Dec 8, 2015 at 16:07

leonz · Accepted Answer · 2015-12-08 16:09:59Z

1

itemfeatures has to be initialized just before for loop each time you read from userfeatures. Otherwise your itemfeatures is fully read after first while iteration

answered Dec 8, 2015 at 16:09

leonz

1311 silver badge4 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Arnaud · Accepted Answer · 2015-12-08 16:16:12Z

1

As people stated, your for loop reads the second file entirely, so you have to read it again each time.

So re-create its Reader before the for loop, and also close it after the for loop.

To put it simply, each time you read one line from File 1, you have to open, read entirely, and close File 2 :

BufferedReader userfeatures = new BufferedReader(new FileReader("userFeatureVectorsTest.csv"));


while ((Uline = userfeatures.readLine()) != null) 
{

    BufferedReader itemfeatures = new BufferedReader(new FileReader("ItemFeatureVectorsTest.csv")); 

    for (String Iline = itemfeatures.readLine(); Iline != null; Iline = itemfeatures.readLine()) 
    {           
         System.out.println(intersect(Uline, Iline).size()); 
         System.out.println(union(Uline, Iline).size());  
    }

   itemfeatures.close();
}
userfeatures.close();

}

answered Dec 8, 2015 at 16:16

Arnaud

17.6k3 gold badges33 silver badges46 bronze badges

1 Comment

mOna Over a year ago

I just accepted the answer, but thanks a lot for the time and effort :)

Collectives™ on Stack Overflow

java outer while loop is not iterating

2 Answers 2

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related