autoboxing

I am struggling with a problem, which I can't understand why it doesn't work. How do I pass a variable through the double obj and convert to int ? Why does it not work in the top code snippet, but it works in the bottom code snippet below the line? The only difference seems to be adding an extra variable, which is also typed as a double ? //Converting double to int using helper //This doesn't work- gets error message //Cannot invoke intValue() on the primitive type double double doublehelpermethod = 123.65; double doubleObj = new Double( doublehelpermethod); System.out.println("The double

While working with the idea of overriding and overridden methods in Java I have noticed that there is some flexiblity given for the return types of such methods. Here is a bit of theory: "The return type of an overriding method in the derived class can be the same, or a subclass of the return type of the overridden method in the base class. The return type of such an overriding method is known as a covariant return type." Example below supposes that B extends A. Method in A: public Object some_method() {....} Method in B: public Integer some_method() {....} So, we see that some_method() in B

I have a class that extends the LinkedList class. Here's an excerpt of the code: class SortedList<Integer> extends LinkedList<Integer> { int intMethod(Integer integerObject){ return integerObject; } } This is expected to return the auto-unboxed int value. But for some reason, the compiler throws an error that says that the types are incompatible and that the required type was int and the type found was Integer. This works in a different class perfectly fine! What gives? :( This is because you have <Integer> after SortedList . Usually you use T for type parameters: class SortedList<T> , but you

I am manually converting code from Java (1.6) to C# and finding some difficulty with the behaviour of primitives (int and double). In C# it appears that almost all conversions happen automatically List<double> list1 = new List<double>(); // legal, C# double d0 = 3.0; list1.Add(d0); // legal, C# Double dd = 2.3f; // legal, C# list1.Add(dd); // legal, C# List<Double> list2 = new List<Double>(); // legal, C# double d1 = 3.0; list2.Add(d1); // legal, C# list2.Add(2.0); // legal, C# double d2 = list2.get(0); // legal, C# but in Java only some are allowed List<double> list1 = new ArrayList<double>()