如何为通用接口类型变量再现java编译/运行时错误，这些变量可能不是同时有两个param接口的子类型？ [英] How to reproduce java compile/runtime error for generic interface type variables that may not be a subtype of two param interfaces at same time?

问题描述

我正在阅读 Java SE 6规范

a>，然后发现一些我无法复制的令人困惑的东西：

类型变量不能同时 是两个接口类型的子类型，它们是相同通用接口的不同参数化。

我写了下面的代码：

 接口奇数{} 
 
接口偶{} 
 
接口奇怪的扩展奇数，偶{} 
 
接口InterfaceOne< O扩展奇数，E扩展偶数> {} 
 
接口InterfaceTwo< O扩展奇数，E扩展偶数>扩展奇数，偶{} 
 
 public class Test {
 public static void main（String [] args）{
 //期望编译错误
 InterfaceOne< Strange，奇怪> t1 = new InterfaceOne<奇怪，奇怪>（）{}; 
 //期望编译错误
 InterfaceTwo< Strange，InterfaceTwo> t2 = new InterfaceTwo< Strange，InterfaceTwo>（）{}; 
 System.out.println（+ t1 + t2）; 
 
 
 
 
 $ b $ p 
 $ b 
上面的代码应该不会编译，但是它确实如此。
 
 
 
如何重现由规格预测的错误？  
 
解决方案
据我所知，泛型类型不能绑定到两个或多个接口，其中这些接口从使用泛型参数的另一个接口扩展而来，绑定的接口对泛型使用不同的类型。我已经写了一个这样的例子： 
 
 
  interface简单< T> {T aMethod（）; } 
接口SimpleString扩展简单< String> {} 
接口SimpleInteger扩展简单<整数> {} 
 public class CompilerError {
 public< T extends SimpleString& SimpleInteger> void（here interesting）{
 System.out.println（interesting.aMethod（））; 
 
 
 $ / code> 
使用javac 1.6.0_32-ea，以下编译器错误：
 
 
  CompilerError.java:5：简单不能用不同的参数继承：< java.lang.String>和< java.lang.Integer> 
 public< T扩展SimpleString& SimpleInteger>在这里无效（T有趣）{
 ^ 
 1错误
  
 
I was reading the Java SE 6 specs and then found some confusing stuff that a I can't reproduce:

  
A type variable may not at the same time be a subtype of two interface types which are different parameterizations of the same generic interface.
I wrote the following code:
interface Odd {}

interface Even {}

interface Strange extends Odd, Even {}

interface InterfaceOne<O extends Odd, E extends Even> {}

interface InterfaceTwo<O extends Odd, E extends Even> extends Odd, Even {}

public class Test {
    public static void main(String[] args) {
        //Expecting compilation error
        InterfaceOne<Strange, Strange> t1 = new InterfaceOne<Strange, Strange>(){};
        //Expecting compilation error
        InterfaceTwo<Strange, InterfaceTwo> t2 = new InterfaceTwo<Strange, InterfaceTwo>(){};
        System.out.println("" + t1 + t2);
    }
}
The code above is supposed to do not compile, but it does.


How to reproduce the error predicted by specification?
解决方案
From what I understand, the generic type cannot be bound to two or more interfaces where these interfaces extend from another interface that employs a generic argument and the bound interfaces use different type for the generic. I've wrote an example of this:
interface Simple<T> { T aMethod(); }
interface SimpleString extends Simple<String> {}
interface SimpleInteger extends Simple<Integer> {}
public class CompilerError {
    public <T extends SimpleString & SimpleInteger> void here(T interesting) {
        System.out.println(interesting.aMethod());
    }
}
Using javac 1.6.0_32-ea, this brings me the following compiler error
CompilerError.java:5: Simple cannot be inherited with different arguments: <java.lang.String> and <java.lang.Integer>
        public <T extends SimpleString & SimpleInteger> void here(T interesting) {
                ^
1 error


                        
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