Attachment 22429 Details for Bug 98538 – Full source code that exhibits compilation errors

Full source code that exhibits compilation errors

TestGenerics.java (text/plain), 2.91 KB, created by Matt McHenry

on 2005-06-06 11:59:04 EDT

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Creator: Matt McHenry

Created: 2005-06-06 11:59:04 EDT

Size: 2.91 KB

patch

obsolete

>//*********************************************************************
>//
>//                        Copyright (C) 2005
>//                      Carnegie Learning Inc.
>//
>//                       All Rights Reserved.
>//
>//This program is the subject of trade secrets and intellectual
>//property rights owned by Carnegie Learning.
>//
>//This legend must continue to appear in the source code despite
>//modifications or enhancements by any party.
>//
>//*********************************************************************
>
>/*
>  $Id$
>  $Name$
>*/
>
>package cl.sdk.common.testcode;
>
>import java.util.Collections;
>import java.util.List;
>
>public class TestGenerics {
>
>	/**Subclasses are parameterized by their own type*/
>	private static abstract class SelfType<T extends SelfType<T>>{
>		public abstract T getThis();
>	}
>
>	/**Supertype inherits directly from the parameterized SelfType*/
>	private static class SuperType extends SelfType<SuperType>{
>		@Override
>		public SuperType getThis(){
>			return this;
>		}
>	}
>
>	/**Subtype inherits indirectly from the parameterized SelfType*/
>	private static class SubType extends SuperType{}
>
>	/**Creates a list containing a single SelfType*/
>	public static <T extends SelfType<T>> List<T> makeSingletonList(T t){
>		return Collections.singletonList(t);
>	}
>
>	/**
>	 * Creates a list containing a single SelfType, allowing the list's
>	 * element-type to be a supertype of the type of its single element
>	 */
>	public static <T extends SelfType<T>,S extends T> List<T> makeSingletonList2(S s){
>		return Collections.singletonList((T)s);
>	}
>
>	public static void main(String[] args){
>		/*making lists of super types works fine ...*/
>		makeSingletonList(new SuperType());
>		List<SuperType> lsup = makeSingletonList(new SuperType());
>
>		/*but we can't make a list of sub types; seems weird ...*/
>		List<SubType> lsub = makeSingletonList(new SubType()); //ERROR
>		/*can't even call it w/o assigning the return value:*/
>		makeSingletonList(new SubType()); //ERROR
>
>
>		/*so instead, we should be able to make lists of super type containing sub type elements*/
>		makeSingletonList2(new SubType()); //ERROR
>		/*even if we assign the return value:*/
>		lsup = makeSingletonList2(new SubType()); // ERROR (eclipse is okay with this though)
>		/*this still doesn't work either:*/
>		lsub = makeSingletonList2(new SubType()); // ERROR
>
>		/*we can make lists of super type this way though*/
>		makeSingletonList2(new SuperType()); // (eclipse doesn't like this though)
>		/*also ok if we assign the return value*/
>		lsup = makeSingletonList2(new SuperType());
>	}
>}
>
>interface FooInterface{}
>
>enum FooEnum implements FooInterface{FOO}
>
>class FooParam<P extends Enum<P> & FooInterface>{}
>
>class FooTest{
>	public static void main(String[] args){
>		FooParam unparam = null;
>		method(unparam);
>	}
>	
>	public static <P extends Enum<P> & FooInterface> void method(FooParam<P> fooparam){
>		
>	}
>}

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Attachments on bug 98538: 22429 | 23536 | 23598