CODEWITHSUNDEEP
javastreaminputstream
Turakar
Turakar

Reputation: 190

How to use a custom method of a FilterInputStream inside another FilterInputStream

I have two streams extending the FilterInputStream class. A is reading doubles from the stream and B shall take those doubles and apply a random noise on them. The question is about how to implement the second stream correctly, so B has access to the custom function of A returning doubles. The chaining shall be as follows:

Source ----> A ----> double ----> B ----> doubles with noise

Best Regards, Turakar

Upvotes: 0

Views: 126

Answers (1)

Tagir Valeev
Tagir Valeev

Reputation: 100279

A FilteredInputStream seems to be not very suitable for your problem as InputStream represents a sequence of bytes, but what you need is the sequence of double numbers. One possible alternative is to implement the Iterator interface instead. Thus A would become:

import java.io.InputStream;
import java.util.Iterator;
import java.util.Scanner;

public class DoubleIterator implements Iterator<Double> {
    private Scanner scanner;

    public DoubleIterator(InputStream is) {
        scanner = new Scanner(is);

    }

    @Override
    public boolean hasNext() {
        return scanner.hasNextDouble();
    }

    @Override
    public Double next() {
        return scanner.nextDouble();
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException();
    }
}

And B would become 

import java.util.Iterator;
import java.util.Random;

public class NoiseIterator implements Iterator<Double> {
    Random r = new Random();
    private Iterator<Double> source;

    public NoiseIterator(Iterator<Double> source) {
        this.source = source;
    }

    @Override
    public boolean hasNext() {
        return source.hasNext();
    }

    @Override
    public Double next() {
        return source.next()+r.nextGaussian();
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException();
    }
}

These classes can be used in the following manner:

String s = "1 56 123 30 0";

Iterator<Double> it = new DoubleIterator(new ByteArrayInputStream(s.getBytes()));
while(it.hasNext()) {
    System.out.println(it.next());
}
it = new NoiseIterator(new DoubleIterator(new ByteArrayInputStream(s.getBytes())));
while(it.hasNext()) {
    System.out.println(it.next());
}

Typical output:

1.0
56.0
123.0
30.0
0.0
-0.011797617285828732
55.71721599815757
123.33995522117877
29.16152453760448
-0.9614750776766922

Upvotes: 1

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