1 /* 2 * Copyright 2002 Sun Microsystems, Inc. All Rights Reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, 20 * CA 95054 USA or visit www.sun.com if you need additional information or 21 * have any questions. 22 */ 23 24 /* 25 * @test 26 * @bug 4509267 27 * @summary generics: parametric exception type versus overriding 28 * @author gafter 29 * 30 * @compile -source 1.5 ParametricException.java 31 */ 32 33 import java.io.*; 34 35 abstract class AChurchBoolean { 36 public abstract <Return, Parameter, Throws extends Throwable> 37 Return accept(IVisitor<Return, Parameter, Throws> visitor, Parameter parameter) throws Throws; 38 39 public interface IVisitor<Return, Parameter, Throws extends Throwable> { 40 public Return caseTrue(Parameter parameter) throws Throws; 41 public Return caseFalse(Parameter parameter) throws Throws; 42 } 43 } 44 45 class TrueChurchBoolean extends AChurchBoolean { 46 private static TrueChurchBoolean instance = new TrueChurchBoolean(); 47 private TrueChurchBoolean() {} 48 public static TrueChurchBoolean singleton() { 49 return instance; 50 } 51 public <Return, Parameter, Throws extends Throwable> 52 Return accept(IVisitor<Return, Parameter, Throws> visitor, Parameter parameter) throws Throws { 53 return visitor.caseTrue(parameter); 54 } 55 } 56 57 class FalseChurchBoolean extends AChurchBoolean { 58 private static FalseChurchBoolean instance = new FalseChurchBoolean(); 59 private FalseChurchBoolean() {} 60 public static FalseChurchBoolean singleton() { 61 return instance; 62 } 63 public <Return, Parameter, Throws extends Throwable> 64 Return accept(IVisitor<Return, Parameter, Throws> visitor, Parameter parameter) throws Throws { 65 return visitor.caseFalse(parameter); 66 } 67 } 68 69 class Pair<T,U> { 70 private T first; 71 private U second; 72 Pair(T first, U second) { 73 this.first = first; 74 this.second = second; 75 } 76 T getFirst() { 77 return first; 78 } 79 U getSecond() { 80 return second; 81 } 82 } 83 84 // Perhaps a bit of a toy example, but relevant nonetheless. 85 class ChurchBooleanTest { 86 private AChurchBoolean bool; 87 public ChurchBooleanTest(AChurchBoolean bool) { 88 this.bool = bool; 89 } 90 public AChurchBoolean readIf(File file, byte[] output) throws IOException { 91 return bool.accept(new AChurchBoolean.IVisitor<AChurchBoolean, Pair<File, byte[]>, IOException>() { 92 public AChurchBoolean caseTrue(Pair<File, byte[]> parameter) throws IOException { 93 FileInputStream input = new FileInputStream(parameter.getFirst()); // throws 94 input.read(parameter.getSecond()); // throws 95 input.close(); // throws 96 return TrueChurchBoolean.singleton(); 97 } 98 public AChurchBoolean caseFalse(Pair<File, byte[]> parameter) throws IOException { 99 return FalseChurchBoolean.singleton(); 100 } 101 }, new Pair<File, byte[]>(file, output)); 102 } 103 }