1

The task is to get all the lines from the file except the lines starting with #, using only the cactoos library. I got the following solution:

        Iterable<Text> data =
            new Filtered(
                    (Func<Text, Boolean>) text -> !text.asString().startsWith("#"),
                    new Split(
                            new TextOf(file),
                            new TextOf("\\n")
                    )
            );

In this solution, I do not like the filtering function, in which I use the startsWith method directly. In cactoos, I did not find a single object that checks that a string begins with a character. And the startsWith call violates the principle of elegant objects, that everything should be an object.

One of the solutions that I see is to write an object like

import org.cactoos.Scalar;
import org.cactoos.Text;
import org.cactoos.text.TextOf;

public final class StartsWith implements Scalar<Boolean> {
    private final Text origin;
    private final Text prefix;

    public StartsWith(String origin, String prefix) {
        this(new TextOf(origin), new TextOf(prefix));
    }

    public StartsWith(Text origin, Text prefix) {
        this.origin = origin;
        this.prefix = prefix;
    }

    @Override
    public Boolean value() throws Exception {
        return origin.asString().startsWith(prefix.asString());
    }
}

Is it possible to do this with only the cactoos library classes?

Which solution would you prefer?

Aleksandr Gubin
  • 11
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1 Answers1

1

StartsWith is already present in cactoos, though it's Scalar<Boolean>.

new Filtered<>(
    new Split(
        new TextOf(file),
        new TextOf("[\r\n]+")
    ),
    x -> new Not(new StartsWith(x, new TextOf("#")))
)
andreoss
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