| /* |
| * Copyright (c) 2002, 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 4509267 |
| * @summary generics: parametric exception type versus overriding |
| * @author gafter |
| * |
| * @compile ParametricException.java |
| */ |
| |
| import java.io.*; |
| |
| abstract class AChurchBoolean { |
| public abstract <Return, Parameter, Throws extends Throwable> |
| Return accept(IVisitor<Return, Parameter, Throws> visitor, Parameter parameter) throws Throws; |
| |
| public interface IVisitor<Return, Parameter, Throws extends Throwable> { |
| public Return caseTrue(Parameter parameter) throws Throws; |
| public Return caseFalse(Parameter parameter) throws Throws; |
| } |
| } |
| |
| class TrueChurchBoolean extends AChurchBoolean { |
| private static TrueChurchBoolean instance = new TrueChurchBoolean(); |
| private TrueChurchBoolean() {} |
| public static TrueChurchBoolean singleton() { |
| return instance; |
| } |
| public <Return, Parameter, Throws extends Throwable> |
| Return accept(IVisitor<Return, Parameter, Throws> visitor, Parameter parameter) throws Throws { |
| return visitor.caseTrue(parameter); |
| } |
| } |
| |
| class FalseChurchBoolean extends AChurchBoolean { |
| private static FalseChurchBoolean instance = new FalseChurchBoolean(); |
| private FalseChurchBoolean() {} |
| public static FalseChurchBoolean singleton() { |
| return instance; |
| } |
| public <Return, Parameter, Throws extends Throwable> |
| Return accept(IVisitor<Return, Parameter, Throws> visitor, Parameter parameter) throws Throws { |
| return visitor.caseFalse(parameter); |
| } |
| } |
| |
| class Pair<T,U> { |
| private T first; |
| private U second; |
| Pair(T first, U second) { |
| this.first = first; |
| this.second = second; |
| } |
| T getFirst() { |
| return first; |
| } |
| U getSecond() { |
| return second; |
| } |
| } |
| |
| // Perhaps a bit of a toy example, but relevant nonetheless. |
| class ChurchBooleanTest { |
| private AChurchBoolean bool; |
| public ChurchBooleanTest(AChurchBoolean bool) { |
| this.bool = bool; |
| } |
| public AChurchBoolean readIf(File file, byte[] output) throws IOException { |
| return bool.accept(new AChurchBoolean.IVisitor<AChurchBoolean, Pair<File, byte[]>, IOException>() { |
| public AChurchBoolean caseTrue(Pair<File, byte[]> parameter) throws IOException { |
| FileInputStream input = new FileInputStream(parameter.getFirst()); // throws |
| input.read(parameter.getSecond()); // throws |
| input.close(); // throws |
| return TrueChurchBoolean.singleton(); |
| } |
| public AChurchBoolean caseFalse(Pair<File, byte[]> parameter) throws IOException { |
| return FalseChurchBoolean.singleton(); |
| } |
| }, new Pair<File, byte[]>(file, output)); |
| } |
| } |