| /* |
| * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| /* |
| * @test |
| * @bug 8003280 |
| * @summary Add lambda tests |
| * use method reference to sort list elements by field |
| * @author Brian Goetz |
| * @author Maurizio Cimadamore |
| * @run main MethodReference01 |
| */ |
| |
| import java.util.*; |
| |
| public class MethodReference01 { |
| |
| interface Getter<U, T> { |
| public U get(T t); |
| } |
| |
| static class Foo { |
| private Integer a; |
| private String b; |
| |
| Foo(Integer a, String b) { |
| this.a = a; |
| this.b = b; |
| } |
| |
| static Integer getA(Foo f) { return f.a; } |
| static String getB(Foo f) { return f.b; } |
| } |
| |
| public static <T, U extends Comparable<? super U>> |
| void sortBy(List<T> s, final Getter<U, T> getter) { |
| Collections.sort(s, new Comparator<T>() { |
| public int compare(T t1, T t2) { |
| return getter.get(t1).compareTo(getter.get(t2)); |
| } |
| }); |
| }; |
| |
| public static void main(String[] args) { |
| List<Foo> c = new ArrayList<Foo>(); |
| c.add(new Foo(2, "Hello3!")); |
| c.add(new Foo(3, "Hello1!")); |
| c.add(new Foo(1, "Hello2!")); |
| checkSortByA(c); |
| checkSortByB(c); |
| } |
| |
| static void checkSortByA(List<Foo> l) { |
| sortBy(l, Foo::getA); |
| int oldA = -1; |
| for (Foo foo : l) { |
| if (foo.a.compareTo(oldA) < 1) { |
| throw new AssertionError(); |
| } |
| } |
| } |
| |
| static void checkSortByB(List<Foo> l) { |
| sortBy(l, Foo::getB); |
| String oldB = ""; |
| for (Foo foo : l) { |
| if (foo.b.compareTo(oldB) < 1) { |
| throw new AssertionError(); |
| } |
| } |
| } |
| } |