aoqi@0: /*
aoqi@0:  * Copyright (c) 2002, 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 4509267
aoqi@0:  * @summary generics: parametric exception type versus overriding
aoqi@0:  * @author gafter
aoqi@0:  *
aoqi@0:  * @compile  ParametricException.java
aoqi@0:  */
aoqi@0: 
aoqi@0: import java.io.*;
aoqi@0: 
aoqi@0: abstract class AChurchBoolean {
aoqi@0:     public abstract <Return, Parameter, Throws extends Throwable>
aoqi@0:     Return accept(IVisitor<Return, Parameter, Throws> visitor, Parameter parameter) throws Throws;
aoqi@0: 
aoqi@0:     public interface IVisitor<Return, Parameter, Throws extends Throwable> {
aoqi@0:         public Return caseTrue(Parameter parameter) throws Throws;
aoqi@0:         public Return caseFalse(Parameter parameter) throws Throws;
aoqi@0:     }
aoqi@0: }
aoqi@0: 
aoqi@0: class TrueChurchBoolean extends AChurchBoolean {
aoqi@0:     private static TrueChurchBoolean instance = new TrueChurchBoolean();
aoqi@0:     private TrueChurchBoolean() {}
aoqi@0:     public static TrueChurchBoolean singleton() {
aoqi@0:         return instance;
aoqi@0:     }
aoqi@0:     public <Return, Parameter, Throws extends Throwable>
aoqi@0:     Return accept(IVisitor<Return, Parameter, Throws> visitor, Parameter parameter) throws Throws {
aoqi@0:         return visitor.caseTrue(parameter);
aoqi@0:     }
aoqi@0: }
aoqi@0: 
aoqi@0: class FalseChurchBoolean extends AChurchBoolean {
aoqi@0:     private static FalseChurchBoolean instance = new FalseChurchBoolean();
aoqi@0:     private FalseChurchBoolean() {}
aoqi@0:     public static FalseChurchBoolean singleton() {
aoqi@0:         return instance;
aoqi@0:     }
aoqi@0:     public <Return, Parameter, Throws extends Throwable>
aoqi@0:     Return accept(IVisitor<Return, Parameter, Throws> visitor, Parameter parameter) throws Throws {
aoqi@0:         return visitor.caseFalse(parameter);
aoqi@0:     }
aoqi@0: }
aoqi@0: 
aoqi@0: class Pair<T,U> {
aoqi@0:     private T first;
aoqi@0:     private U second;
aoqi@0:     Pair(T first, U second) {
aoqi@0:         this.first = first;
aoqi@0:         this.second = second;
aoqi@0:     }
aoqi@0:     T getFirst() {
aoqi@0:         return first;
aoqi@0:     }
aoqi@0:     U getSecond() {
aoqi@0:         return second;
aoqi@0:     }
aoqi@0: }
aoqi@0: 
aoqi@0: // Perhaps a bit of a toy example, but relevant nonetheless.
aoqi@0: class ChurchBooleanTest {
aoqi@0:     private AChurchBoolean bool;
aoqi@0:     public ChurchBooleanTest(AChurchBoolean bool) {
aoqi@0:         this.bool = bool;
aoqi@0:     }
aoqi@0:     public AChurchBoolean readIf(File file, byte[] output) throws IOException {
aoqi@0:         return bool.accept(new AChurchBoolean.IVisitor<AChurchBoolean, Pair<File, byte[]>, IOException>() {
aoqi@0:             public AChurchBoolean caseTrue(Pair<File, byte[]> parameter) throws IOException {
aoqi@0:                 FileInputStream input = new FileInputStream(parameter.getFirst()); // throws
aoqi@0:                 input.read(parameter.getSecond()); // throws
aoqi@0:                 input.close(); // throws
aoqi@0:                 return TrueChurchBoolean.singleton();
aoqi@0:             }
aoqi@0:             public AChurchBoolean caseFalse(Pair<File, byte[]> parameter) throws IOException {
aoqi@0:                 return FalseChurchBoolean.singleton();
aoqi@0:             }
aoqi@0:         }, new Pair<File, byte[]>(file, output));
aoqi@0:     }
aoqi@0: }