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  1. public class Main {
  2.  
  3.     static class Animal { }
  4.     static class Dog extends Animal { }
  5.     static class Cat extends Animal { }
  6.  
  7.     public <T extends Animal>T get(Class<T> type) {
  8.     // get the animals somehow
  9.     java.util.List<Animal> animals = getList();
  10.         for(Animal animal : animals) {
  11.             if(type.isInstance(animal)) {
  12.                 // this casting is safe
  13.                 return (T)animal;
  14.             }
  15.         }
  16.         // if not found
  17.         return null;
  18.     }
  19.  
  20.     private java.util.List<Animal> getList() {
  21.         return java.util.Arrays.asList(new Cat(), new Dog());
  22.     }
  23.  
  24.     public void test() {
  25.         Dog dog = get(Dog.class); // ok
  26.         Cat cat = get(Dog.class); // ok, expected compiler error
  27.     }
  28.  
  29.     public static void main(String[] args) {
  30.  
  31.         new Main().test();
  32.  
  33.         System.out.println("done");
  34.     }
  35. }
Compilation error #stdin compilation error #stdout 0s 0KB
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stdin
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Standard input is empty
compilation info 
Main.java:26: incompatible types
found   : Main.Dog
required: Main.Cat
        Cat cat = get(Dog.class); // ok, expected compiler error
                     ^
Note: Main.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
1 error
stdout
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Standard output is empty
https://ideone.com/gqzkkf
language:
Java (HotSpot 12)
created:
12 years ago
visibility:
public

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