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22 results

ParametricException.java

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  • ParametricException.java 3.69 KiB
    /*
     * 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));
        }
    }