autoboxing

Is there any way to use autoboxing for the classes I create? For example, I have this subclass of Number . public class UnsignedInteger extends Number { int n; public UnsignedInteger(int n) { if(n >= 0) this.n = n; else throw new IllegalArgumentException("Only positive integers are supported"); } } Now, UnsignedInteger i = new UnsignedInteger(88); works perfectly fine, but is there any way to make this compile : UnsignedInteger i = 88; ? It won't for me. Thanks in advance! rgettman In short, no. There's no way to get that to compile. Java only defines a limited set of pre-defined boxing

I want to compare two Long objects values using if conditions. When these values are less than 128 , the if condition works properly, but when they are greater than or equal to 128 , comparison fails. Example: Long num1 = 127; Long num2 = 127; if (num1 == num2) { // Works ok } Comparison on the code above works properly, but fails in the code below: Long num1 = 128; Long num2 = 128; if (num1 == num2) { // Does NOT work } Why is there a problem in comparing Long variables with values greater than 127 ? If the variables data types are changed to long primitives , then the comparisons work for

I tripped across a really strange NullPointerException the other day caused by an unexpected type-cast in the ternary operator. Given this (useless exemplary) function: Integer getNumber() { return null; } I was expecting the following two code segments to be exactly identical after compilation: Integer number; if (condition) { number = getNumber(); } else { number = 0; } vs. Integer number = (condition) ? getNumber() : 0; . Turns out, if condition is true , the if -statement works fine, while the ternary opration in the second code segment throws a NullPointerException . It seems as though

I have a method like this: public static <T> boolean isMemberOf(T item, T[] set) { for (T t : set) { if (t.equals(item)) { return true; } } return false; } Now I try to call this method using a char for T : char ch = 'a'; char[] chars = new char[] { 'a', 'b', 'c' }; boolean member = isMemberOf(ch, chars); This doesn't work. I would expect the char and char[] to get autoboxed to Character and Character[] , but that doesn't seem to happen. Any insights? There is no autoboxing for arrays, only for primitives. I believe this is your problem. Why would char[] be boxed to Character[] ? Arrays are

The following code throws NullPointerException : int num = Integer.getInteger("123"); Is my compiler invoking getInteger on null since it's static? That doesn't make any sense! What's happening? polygenelubricants The Big Picture There are two issues at play here: Integer getInteger(String) doesn't do what you think it does It returns null in this case the assignment from Integer to int causes auto-unboxing Since the Integer is null , NullPointerException is thrown To parse (String) "123" to (int) 123 , you can use e.g. int Integer.parseInt(String) . References Java Language Guide/Autoboxing

Why does this throw NullPointerException public static void main(String[] args) throws Exception { Boolean b = true ? returnsNull() : false; // NPE on this line. System.out.println(b); } public static Boolean returnsNull() { return null; } while this doesn't public static void main(String[] args) throws Exception { Boolean b = true ? null : false; System.out.println(b); // null } ? The solution is by the way to replace false by Boolean.FALSE to avoid null being unboxed to boolean --which isn't possible. But that isn't the question. The question is why ? Are there any references in JLS which