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Java Generics – No Exception

Java Generics - No Exception

This topic is about Java Generics – No Exception.

A generic class is not allowed to extend the Throwable class directly or indirectly.

//The generic class Box<T> may not subclass java.lang.Throwable
class Box<T> extends Exception {}

//The generic class Box<T> may not subclass java.lang.Throwable
class Box1<T> extends Throwable {}

A method is not allowed to catch an instance of a type parameter.

public static <T extends Exception, J> 
   void execute(List<J> jobs) {
      try {
         for (J job : jobs) {}
  
         // compile-time error
         //Cannot use the type parameter T in a catch block
      } catch (T e) { 
         // ...
   }
}

Type parameters are allowed in a throws clause.

class Box<T extends Exception>  {
   private int t;

   public void add(int t) throws T {
      this.t = t;
   }

   public int get() {
      return t;
   }   
}

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