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/*
* 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));
}
}
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