Function.java

package br.com.ngi.ginga.business.util.seq;

/**
 * Copyright (C) 2015 - NG Informática
 *
 * @author Marcelo Camargo
 * @since 08/12/2015
 */
public interface Function<Ret, Arg> {
    Ret call(Arg arg);
}

Seq.java

package br.com.ngi.ginga.business.util.seq;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.Callable;

/**
 * Copyright (C) 2015 - NG Informática
 *
 * @author Marcelo Camargo
 * @since 08/12/2015
 */
public class Seq<T> {
    private List<T> value;

    @SafeVarargs
    public Seq(T ...args) {
        value = new ArrayList<>();
        Collections.addAll(value, args);
    }

    public void add(T item) {
        this.value.add(item);
    }

    public <Ret> Seq<Ret> map(Function<Ret, T> fn) {
        Seq<Ret> buffer = new Seq();
        for (T item : this.value) {
            buffer.add(fn.call(item));
        }
        return buffer;
    }

    public Seq<T> filter(Function<Boolean, T> fn) {
        Seq<T> buffer = new Seq<>();
        for (T item : this.value) {
            if (fn.call(item)) {
                buffer.add(item);
            }
        }
        return buffer;
    }

    public ArrayList<T> toArrayList() {
        return (ArrayList<T>) this.value;
    }
}