Example usage for java.util.stream Collector of

Introduction

In this page you can find the example usage for java.util.stream Collector of.

Prototype

public static <T, R> Collector<T, R, R> of(Supplier<R> supplier, BiConsumer<R, T> accumulator,
        BinaryOperator<R> combiner, Characteristics... characteristics) 

Source Link

Document

Returns a new Collector described by the given supplier , accumulator , and combiner functions.

Usage

From source file:org.briljantframework.data.Collectors.java

/**
 * Performs a transformation operation, mapping each element to a new value, adding it to the
 * {@code Vector.Builder} finishing it constructs a new {@code Vector}.
 *
 * @param supplier supply the vector builder
 * @param function the mapper/*from w  w w  .  jav  a2 s . c  o m*/
 * @param <T> the input type
 * @param <O> the output type
 * @return a transformation aggregator
 */
public static <T, O> Collector<T, ?, Vector> map(Supplier<Vector.Builder> supplier,
        Function<? super T, ? extends O> function) {
    return Collector.of(supplier, (acc, v) -> acc.add(function.apply(v)),
            (Vector.Builder left, Vector.Builder right) -> {
                left.addAll(right);
                return left;
            }, Vector.Builder::build);
}

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From source file:org.briljantframework.data.Collectors.java

/**
 * Returns an aggregator that filter values.
 *
 * @param supplier the vector builder//ww w. j a  va  2s  . c  o m
 * @param predicate the predicate. If {@code true} include value.
 * @param <T> the input type
 * @return a filtering aggregator
 */
public static <T> Collector<T, ?, Vector> filter(Supplier<Vector.Builder> supplier, Predicate<T> predicate) {
    return Collector.of(supplier, (acc, v) -> {
        if (predicate.test(v)) {
            acc.add(v);
        }
    }, (Vector.Builder left, Vector.Builder right) -> {
        left.addAll(right);
        return left;
    }, Vector.Builder::build);
}

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From source file:org.briljantframework.data.Collectors.java

/**
 * @param copies the number of copies of each element
 * @return an aggregator that repeats each value {@code copies} times.
 *//*  w ww . j av a 2s  .  c o m*/
public static <T> Collector<T, ?, Vector> each(Supplier<Vector.Builder> vb, int copies) {
    return Collector.of(vb, (acc, v) -> {
        for (int i = 0; i < copies; i++) {
            acc.add(v);
        }
    }, (Vector.Builder left, Vector.Builder right) -> {
        left.addAll(right);
        return left;
    }, Vector.Builder::build);
}

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From source file:org.briljantframework.data.Collectors.java

public static <T> Collector<T, ?, Vector> repeat(Supplier<Vector.Builder> vb, int copies) {
    return Collector.of(vb, Vector.Builder::add, (Vector.Builder left, Vector.Builder right) -> {
        left.addAll(right);/*  www  .j  a v  a 2 s.com*/
        return left;
    }, (v) -> {
        Vector temp = v.getView();
        int size = temp.size();
        for (int i = 1; i < copies; i++) {
            for (int j = 0; j < size; j++) {
                v.add(temp, j);
            }
        }
        return v.build();
    });
}

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From source file:org.briljantframework.data.Collectors.java

public static <T> Collector<T, ?, Vector> unique() {
    return Collector.of(HashSet::new, HashSet::add, (ts, ts2) -> {
        ts.addAll(ts2);//from   w ww. j av  a 2 s  . c o m
        return ts;
    }, ts -> new TypeInferenceVectorBuilder().addAll(ts).build());
}

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From source file:org.briljantframework.data.Collectors.java

public static <T> Collector<T, ?, Integer> nunique() {
    return Collector.of(HashSet::new, HashSet::add, (left, right) -> {
        left.addAll(right);/*w  ww .  j a  v  a2  s .c om*/
        return left;
    }, HashSet::size);
}

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From source file:org.briljantframework.data.Collectors.java

public static Collector<Object, ?, Vector> factorize() {
    class Factorize {

        Map<Object, Integer> map = new HashMap<>();
        Vector.Builder builder = Vector.Builder.of(Integer.class);
        int highest = 0;
    }//w w  w  . j  a  va  2s .c o  m

    // TODO: refactor into a real state-less collector
    Factorize factorize = new Factorize();
    return Collector.of(() -> factorize, (Factorize acc, Object value) -> {
        synchronized (factorize) {
            Integer code = acc.map.get(value);
            if (code == null) {
                code = acc.highest;
                acc.map.put(value, code);
                acc.highest++;
            }
            acc.builder.add(code);
        }
    }, (left, right) -> left, (acc) -> acc.builder.build());
}

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From source file:org.briljantframework.data.Collectors.java

public static Collector<Number, ?, StatisticalSummary> statisticalSummary() {
    return Collector.of(FastStatistics::new, (FastStatistics a, Number v) -> {
        if (!Is.NA(v)) {
            a.addValue(v.doubleValue());
        }/*from w ww  .  j  a  v a 2  s  .  c o  m*/
    }, (left, right) -> {
        throw new IllegalStateException("Can't collect statistics in parallel");
    }, FastStatistics::getSummary);
}

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From source file:org.briljantframework.data.Collectors.java

/**
 * @return an aggregator that computes the median.
 *//*from   w  ww  .  ja  v  a 2  s  .  c om*/
public static Collector<Number, ?, Double> median() {
    return Collector.of(ArrayList::new, ArrayList::add, (left, right) -> {
        left.addAll(right);
        return left;
    }, (ArrayList<Number> list) -> {
        int size = list.size();
        if (size == 0) {
            return Na.of(Double.class);
        } else if (size == 1) {
            return list.get(0).doubleValue();
        } else if (size == 2) {
            return (list.get(0).doubleValue() + list.get(1).doubleValue()) / 2;
        } else {
            list.sort((a, b) -> Double.compare(a.doubleValue(), b.doubleValue()));
            int index = (size - 1) / 2;
            if (size % 2 == 0) {
                return (list.get(index).doubleValue() + list.get(index + 1).doubleValue()) / 2;
            } else {
                return list.get(index).doubleValue();
            }
        }
    });
}

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From source file:org.briljantframework.data.Collectors.java

public static Collector<Number, ?, Number> max() {
    class MaxBox {

        double value = Double.NEGATIVE_INFINITY;
        boolean hasValue = false;

        void update(double v) {
            if (!Is.NA(v)) {
                hasValue = true;// ww w.j a v  a 2  s. c o  m
                value = Math.max(v, value);
            }
        }
    }

    return Collector.of(MaxBox::new, (a, v) -> a.update(v.doubleValue()), (left, right) -> {
        left.update(right.value);
        return left;
    }, (r) -> r.hasValue ? r.value : Na.DOUBLE);
}

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