Enthuware

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class A
class B extends A
class C extends C

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? extends A --> it's allowed the following classes: A,B or C
? extends B --> it's allowed the following classes: B or C
? extends C --> it's allowed the following classes: C

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? super A --> it's allowed the following classes: A or Object
? super B --> it's allowed the following classes: B, A or Object
? super C --> it's allowed the following classes: C, B, A or Object

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static class Vehicle {}
static class Car extends Vehicle {}


List<? extends Vehicle> vehicless = new ArrayList<Vehicles>();
vehicless.add(new Car()); // if Car is superclass of Vehicle, why this statement does not compile?
vehicless.add(new Vehicle()); // why this statement does not compile?

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List<? super IOException> exceptions = new ArrayList<Exception>();
exceptions.add(new Exception()); // if Exception is superclass of IOException, why this statement does not compile?
exceptions.add(new IOException()); // it's correct because the IOExecption is included in super clause
exceptions.add(new FileNotFoundException()); // if FileNotFoundException is not included in super clause, why this statement is correct?