autoboxing

As Java 5 have autoboxing, why I can't use Comparator to sort primitives? An int wouldn't be wrapped into a Integer ? Arrays.sort(..) have dedicated overloadings for sorting primitive arrays. If you need any special sorting rules apart from the standard ones, I'm afraid you'd have to use autoboxing. In addition to that, you'd have to transform your array to Integer[] , because int[] is not autoboxed. And if you are not talking about arrays, but about collections - then you have no choice - collections can hold only objects. Because you cannot parameterise a Comparator<T> -- or any other

This question already has an answer here: Weird Integer boxing in Java 10 answers I have stumbled upon this in Java (JDK 1.7): Integer a = 100; Integer b = 100; Integer c = 1000; Integer d = 1000; System.out.println(a == b); //true System.out.println(c == d); //false System.out.println(new Integer(100) == new Integer(100)); //false System.out.println(new Integer(1000) == new Integer(1000)); //false The output is: true false false false Why does a==b evaluate to true? What is the reason for this? Is this similar to String internalization? Is this similar to String internalization? Yes -

In "Core java 1" I've read CAUTION: An ArrayList is far less efficient than an int[] array because each value is separately wrapped inside an object. You would only want to use this construct for small collections when programmer convenience is more important than efficiency. But in my software I've already used Arraylist instead of normal arrays due to some requirements, though "The software is supposed to have high performance and after I've read the quoted text I started to panic!" one thing I can change is changing double variables to Double so as to prevent auto boxing and I don't know if

We are using axis2 to generate web-service clients, (I regret this now!). With axis2 command-line tool you can pass switch -Euwc to wrap int into Integer, boolean into Boolean and so on in generated soruces. This is the one way to tell axis2 that its OK for certain int or boolean values to be nillable in schema. My question is how do you set this parameter via POM or other means with Maven to achieve same behaviour with genrated sources? My stackoverflow and google searches aren't revealing much. There's a Jira issue, which seems to be closed by developers without pointing in right direction.

I found a piece of code that after switching from Java 7 to Java 8 stopped compiling. It does not feature any of the new Java 8 stuff like lambda or streams. I narrowed the problematic code down to the following situation: GenericData<Double> g = new GenericData<>(1d); Double d = g == null ? 0 : g.getData(); // type error!!! You can probably guess that GenericData 's constructor has one parameter of that generic type and the getData() method returns just that generic type. (For the complete source code see below.) Now what bothers me is that in Java 7 that code compiled just fine whereas with

I really can'get my head around why the following happens: Double d = 0.0; System.out.println(d == 0); // is true System.out.println(d.equals(0)); // is false ?! This however works as expected: Double d = 0.0; System.out.println(d == 0.0); // true System.out.println(d.equals(0.0)); // true I'm positive that this is related to autoboxing in some way, but I really don't know why 0 would be boxed differently when the == operator is used and when .equals is called . Doesn't this implicitly violate the equals contract ? * It is reflexive: for any non-null reference value * x, x.equals(x) should