CODEWITHSUNDEEP
javajava-8streamjava-stream
Karthikeyan
Karthikeyan

Reputation: 2001

Write a batch String in to file using a Java stream

Am having a List object having String values which i want to write it into a file by batch-by-batch.

In my below code, am having batch value as 4. so, am expecting to write 4 string values into the file from batch-1. Next batch (batch-2) it should write other 4 string values.

But its not working as expected.

Please find the my code below.

public class WriteToFile {
    
    public static void batches(List source, int length) throws IOException {
        if (length <= 0)
            throw new IllegalArgumentException("length = " + length);
        int size = source.size();

        int fullChunks = (size - 1) / length;
            
        try(PrintWriter pw = new PrintWriter(Files.newBufferedWriter(
                Paths.get("C:\\Users\\Karthikeyan\\Desktop\\numbers.txt")))) {
            IntStream.range(0, fullChunks + 1).mapToObj(String::valueOf).forEach(pw::println);
            
    }
    

}

    public static void main(String[] args) throws IOException {
        List<String> list = Arrays.asList("a", "b", "c", "d", "e", "f");

        
        System.out.println("By 4:");
        batches(list, 4);
    }

}

Below contents are writting in my file.

0
1

It should write :

a
b
c
d
e
f

In batch.

Upvotes: -2

Views: 183

Answers (1)

Gerard
Gerard

Reputation: 35

The statement:

int fullChunks = (size - 1) / length;

Will result in 6 - 1 / 4. Because these are ints it is rounded downwards so the result will be 5/4 = 1.

In IntStream you take the range form 0, 2 (to upper limmit is not part of the range) so 2 elements resulting in 0, 1. If you want the value from the list itself than use mapToObj(i -> source.get(i).toString()) instead of .mapToObj(String::valueOf)

It is not clear what you want you want to accomplish with batches, because the results are all written to the same file.

Upvotes: 0

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