fork(1) download
copy 
  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.io.*;
  6.  
  7. /* Name of the class has to be "Main" only if the class is public. */
  8. class Ideone
  9. {
  10. 	public static void main (String[] args) throws java.lang.Exception
  11. 	{
  12. 		// your code goes here
  13.         new Ideone();
  14. 	}
  15.  
  16. 	Ideone() {
  17.         Foo<Bar> fooBar = new Foo<>(Bar.class);
  18.         Foo<Bar2> fooBar2 = new Foo<>(Bar2.class);
  19.         fooBar.say("fooBar", Bar.class);
  20.         fooBar2.say("fooBar2", Bar2.class);
  21.  
  22.         Foo<Bar2> shouldFail = fooBar.fooing(Bar.class);  // this should not work at compile time
  23.         Foo<? extends Bar2> shouldFail2 = fooBar.fooing(Bar.class); // this should not work at compile time
  24.         shouldFail.say("shouldFail", null);
  25.         shouldFail2.say("shouldFail2", null);
  26.  
  27.         // wanted:
  28.         Foo<Bar> barFoo = fooBar2.fooing(Bar.class);
  29.         Foo<? super Bar> barFoo2 = fooBar2.fooing(Bar.class);
  30.         barFoo.say("barFoo", Bar.class);
  31.         barFoo2.say("barFoo2", Bar.class);
  32. 	}
  33.  
  34.     class Foo<T extends Bar> {
  35.         Class<T> myClass;
  36.  
  37.         public Foo(Class<T> clazz) {
  38.             myClass = clazz;
  39.         }
  40.  
  41.         public <S extends Bar> Foo<S> fooing(Class<? super T> clazz) {
  42.             return new Foo(clazz);
  43.         }        
  44.  
  45.         public void say(String pre, Class<?> expected) {
  46.             if (!myClass.equals(expected)) {
  47.                 System.out.print("FAILURE!!! ");
  48.             }
  49.             System.out.println("" + pre + " was: " + myClass.getSimpleName() +
  50.                     "(expected: " + expected + ")");
  51.         }
  52.     }
  53.  
  54.     class Bar {
  55.     }
  56.  
  57.     class Bar2 extends Bar {
  58.     }
  59. }
Success #stdin #stdout 0.08s 380160KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
fooBar was: Bar(expected: class Ideone$Bar)
fooBar2 was: Bar2(expected: class Ideone$Bar2)
FAILURE!!! shouldFail was: Bar(expected: null)
FAILURE!!! shouldFail2 was: Bar(expected: null)
barFoo was: Bar(expected: class Ideone$Bar)
barFoo2 was: Bar(expected: class Ideone$Bar)
https://ideone.com/scBFLc
language:
Java (HotSpot 12)
created:
10 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!