CODEWITHSUNDEEP
optimizationjava-stream
Jegors Čemisovs
Jegors Čemisovs

Reputation: 740

How to properly generate a long stream where one number should be skipped?

The method should return long stream from -n to n except 0. For n = 3 the stream should be -3, -2, -1, 1, 2, 3.

What approach is better?

(1)

public static LongStream getLongStream(int n) {
    return n == 0 
        ? LongStream.empty() 
        : LongStream.concat(
            LongStream.range(-n, 0), 
            LongStream.rangeClosed(1, n));

}

(2)

public static LongStream getLongStream(int n) {
    return LongStream.concat(
            LongStream.range(-n, 0), 
            LongStream.rangeClosed(1, n));

}

Thank you for your comments. I suppose that the second variant is the best way to produce such streams.

Upvotes: 0

Views: 235

Answers (2)

Anonymous
Anonymous

Reputation: 86272

It will be a matter of taste. Take the version that you and in particular your readers — those maintaining your code after you — will prefer. Here’s yet an option. I like to make your requirement one number should be skipped more explicit in the code.

public static LongStream getLongStream(int n) {
    return LongStream.rangeClosed(-n, n).filter(i -> i != 0);
}

To try it out:

    System.out.println(getLongStream(3).boxed().collect(Collectors.toList()));

Output:

[-3, -2, -1, 1, 2, 3]

It’s less runtime efficient than your versions. Holger’s comment seems to indicate that the difference may be great for large values of n, though depending on what you are using the stream for. If concerned, you will need to make your own measurements.

Upvotes: 2

Jegors Čemisovs
Jegors Čemisovs

Reputation: 740

I think that in terms of optimization the second variant is the best one.

public static LongStream getLongStream(long n) {
    return LongStream.concat(
            LongStream.range(-n, 0), 
            LongStream.rangeClosed(1, n));

}

Upvotes: 1

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