1 /*

     2  * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  */

    23 

    24 package org.openjdk.tests.java.util.stream;

    25 

    26 /*

    27  * THE CONTENTS OF THIS FILE HAVE TO BE IN SYNC WITH THE EXAMPLES USED

    28  * IN THE JAVADOC.

    29  *

    30  * @test

    31  * @bug 8231161

    32  * @compile CollectorExample.java

    33  * @summary Compilation test only. Compile code snippets from

    34  * java.util.stream.Collector class-level API documentation

    35  */

    36 

    37 import java.util.*;

    38 import java.util.function.BiConsumer;

    39 import java.util.function.BinaryOperator;

    40 import java.util.function.Function;

    41 import java.util.function.Supplier;

    42 import java.util.stream.Collector;

    43 import java.util.stream.Collectors;

    44 

    45 public class CollectorExample {

    46 

    47     // Empty helper classes

    48 

    49     class Widget {

    50     }

    51 

    52     class Employee {

    53         public int getSalary() {

    54             return 0;    // money isn't everything

    55         }

    56 

    57         public Department getDepartment() {

    58             return new Department();

    59         }

    60     }

    61 

    62     class Department {

    63     }

    64 

    65     <T, A, R> void testSnippet1(Collector<T, A, R> collector, T t1, T t2) {

    66 

    67         Supplier<A> supplier = collector.supplier();

    68         BiConsumer<A, T> accumulator = collector.accumulator();

    69         BinaryOperator<A> combiner = collector.combiner();

    70         Function<A, R> finisher = collector.finisher();

    71 

    72         // Example start

    73         A a1 = supplier.get();

    74         accumulator.accept(a1, t1);

    75         accumulator.accept(a1, t2);

    76         R r1 = finisher.apply(a1);

    77 

    78         A a2 = supplier.get();

    79         accumulator.accept(a2, t1);

    80         A a3 = supplier.get();

    81         accumulator.accept(a3, t2);

    82         R r2 = finisher.apply(combiner.apply(a2, a3));

    83     }

    84 

    85     void testSnippet2() {

    86         Collector<Widget, ?, TreeSet<Widget>> intoSet =

    87                 Collector.of(TreeSet::new, TreeSet::add,

    88                         (left, right) -> { left.addAll(right); return left; });

    89     }

    90 

    91     <T, A, R> void testSnippet3(Collector<T, A, R> collector, Collection<T> data) {

    92         A container = collector.supplier().get();

    93         for (T t : data)

    94             collector.accumulator().accept(container, t);

    95         collector.finisher().apply(container);

    96     }

    97 

    98     void testSnippet4and5() {

    99         Collector<Employee, ?, Integer> summingSalaries

   100                 = Collectors.summingInt(Employee::getSalary);

   101 

   102         Collector<Employee, ?, Map<Department, Integer>> summingSalariesByDept

   103                 = Collectors.groupingBy(Employee::getDepartment, summingSalaries);

   104     }

   105 }