A primitive type is just data. What we call objects, on the other hand, are just pointers to where the data is stored. For example: Integer object = new Integer(3); int number = 3; In this case, object is just a pointer to an Integer object whose value happens to be 3. That is, at … Read more
As gurukulki said, it’s stored on the heap. However, your post suggested a misunderstanding probably due to some well-intentioned person propagating the myth that “primitives always live on the stack”. This is untrue. Local variables have their values on the stack, but not all primitive variables are local… For example, consider this: public class Foo … Read more
There isn’t a way to pass a primitive directly by reference in Java. A workaround is to instead pass a reference to an instance of a wrapper class, which then contains the primitive as a member field. Such a wrapper class could be extremely simple to write for yourself: public class IntRef { public int … Read more
Others have mentioned that certain constructs such as Collections require objects and that objects have more overhead than their primitive counterparts (memory & boxing). Another consideration is: It can be handy to initialize Objects to null or send null parameters into a method/constructor to indicate state or function. This can’t be done with primitives. Many … Read more
It was a Java design decision, and one that some consider a mistake. Containers want Objects and primitives don’t derive from Object. This is one place that .NET designers learned from the JVM and implemented value types and generics such that boxing is eliminated in many cases. In CLR, generic containers can store value types … Read more
I think the best you’d be able to do is use IConvertible as a constraint and do something like: public static operator T +(T x, T y) where T: IConvertible { var type = typeof(T); if (type == typeof(String) || type == typeof(DateTime)) throw new ArgumentException(String.Format(“The type {0} is not supported”, type.FullName), “T”); try { … Read more
Use an NSNumberFormatter: NSNumberFormatter *f = [[NSNumberFormatter alloc] init]; f.numberStyle = NSNumberFormatterDecimalStyle; NSNumber *myNumber = [f numberFromString:@”42″]; If the string is not a valid number, then myNumber will be nil. If it is a valid number, then you now have all of the NSNumber goodness to figure out what kind of number it actually is.
In Joshua Bloch’s Effective Java, Item 5: “Avoid creating unnecessary objects”, he posts the following code example: public static void main(String[] args) { Long sum = 0L; // uses Long, not long for (long i = 0; i <= Integer.MAX_VALUE; i++) { sum += i; } System.out.println(sum); } and it takes 43 seconds to run. … Read more
Basically, requiring a variable to be assigned a value before you read it is a Good Thing. It means you won’t accidentally read something you didn’t intend to. Yes, variables could have default values – but isn’t it better for the compiler to be able to catch your bug instead, if it can prove that … Read more
If you are using java-8 there’s also another way to do this. int[] arr = list.stream().mapToInt(i -> i).toArray(); What it does is: getting a Stream<Integer> from the list obtaining an IntStream by mapping each element to itself (identity function), unboxing the int value hold by each Integer object (done automatically since Java 5) getting the … Read more