aoqi@0: /*
aoqi@0:  * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
aoqi@0:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
aoqi@0:  *
aoqi@0:  * This code is free software; you can redistribute it and/or modify it
aoqi@0:  * under the terms of the GNU General Public License version 2 only, as
aoqi@0:  * published by the Free Software Foundation.
aoqi@0:  *
aoqi@0:  * This code is distributed in the hope that it will be useful, but WITHOUT
aoqi@0:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
aoqi@0:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
aoqi@0:  * version 2 for more details (a copy is included in the LICENSE file that
aoqi@0:  * accompanied this code).
aoqi@0:  *
aoqi@0:  * You should have received a copy of the GNU General Public License version
aoqi@0:  * 2 along with this work; if not, write to the Free Software Foundation,
aoqi@0:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
aoqi@0:  *
aoqi@0:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
aoqi@0:  * or visit www.oracle.com if you need additional information or have any
aoqi@0:  * questions.
aoqi@0:  */
aoqi@0: 
aoqi@0: /*
aoqi@0:  * @test
aoqi@0:  * @bug 8003280
aoqi@0:  * @summary Add lambda tests
aoqi@0:  *  use method reference to sort list elements by field
aoqi@0:  * @author  Brian Goetz
aoqi@0:  * @author  Maurizio Cimadamore
aoqi@0:  * @run main MethodReference01
aoqi@0:  */
aoqi@0: 
aoqi@0: import java.util.*;
aoqi@0: 
aoqi@0: public class MethodReference01 {
aoqi@0: 
aoqi@0:     interface Getter<U, T> {
aoqi@0:         public U get(T t);
aoqi@0:     }
aoqi@0: 
aoqi@0:     static class Foo {
aoqi@0:         private Integer a;
aoqi@0:         private String b;
aoqi@0: 
aoqi@0:         Foo(Integer a, String b) {
aoqi@0:             this.a = a;
aoqi@0:             this.b = b;
aoqi@0:         }
aoqi@0: 
aoqi@0:         static Integer getA(Foo f) { return f.a; }
aoqi@0:         static String getB(Foo f) { return f.b; }
aoqi@0:     }
aoqi@0: 
aoqi@0:     public static <T, U extends Comparable<? super U>>
aoqi@0:            void sortBy(List<T> s, final Getter<U, T> getter) {
aoqi@0:         Collections.sort(s, new Comparator<T>() {
aoqi@0:             public int compare(T t1, T t2) {
aoqi@0:                 return getter.get(t1).compareTo(getter.get(t2));
aoqi@0:             }
aoqi@0:         });
aoqi@0:     };
aoqi@0: 
aoqi@0:     public static void main(String[] args) {
aoqi@0:         List<Foo> c = new ArrayList<Foo>();
aoqi@0:         c.add(new Foo(2, "Hello3!"));
aoqi@0:         c.add(new Foo(3, "Hello1!"));
aoqi@0:         c.add(new Foo(1, "Hello2!"));
aoqi@0:         checkSortByA(c);
aoqi@0:         checkSortByB(c);
aoqi@0:     }
aoqi@0: 
aoqi@0:     static void checkSortByA(List<Foo> l) {
aoqi@0:         sortBy(l, Foo::getA);
aoqi@0:         int oldA = -1;
aoqi@0:         for (Foo foo : l) {
aoqi@0:             if (foo.a.compareTo(oldA) < 1) {
aoqi@0:                 throw new AssertionError();
aoqi@0:             }
aoqi@0:         }
aoqi@0:     }
aoqi@0: 
aoqi@0:     static void checkSortByB(List<Foo> l) {
aoqi@0:         sortBy(l, Foo::getB);
aoqi@0:         String oldB = "";
aoqi@0:         for (Foo foo : l) {
aoqi@0:             if (foo.b.compareTo(oldB) < 1) {
aoqi@0:                 throw new AssertionError();
aoqi@0:             }
aoqi@0:         }
aoqi@0:     }
aoqi@0: }