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