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