Convert an array of primitive longs into a List of Longs
Since Java 8 you can now use streams for that: long[] arr = { 1, 2, 3, 4 }; List<Long> list = Arrays.stream(arr).boxed().collect(Collectors.toList());
boxing
What is boxing and unboxing and what are the trade offs?
Boxed values are data structures that are minimal wrappers around primitive types*. Boxed values are typically stored as pointers to objects on the heap. Thus, boxed values use more memory and take at minimum two memory lookups to access: once to get the pointer, and another to follow that pointer to the primitive. Obviously this … Read more
Why are Python’s arrays slow?
The storage is “unboxed”, but every time you access an element Python has to “box” it (embed it in a regular Python object) in order to do anything with it. For example, your sum(A) iterates over the array, and boxes each integer, one at a time, in a regular Python int object. That costs time. … Read more
Why do we need boxing and unboxing in C#?
Why To have a unified type system and allow value types to have a completely different representation of their underlying data from the way that reference types represent their underlying data (e.g., an int is just a bucket of thirty-two bits which is completely different than a reference type). Think of it like this. You … Read more
How to convert int[] into List in Java?
Streams In Java 8+ you can make a stream of your int array. Call either Arrays.stream or IntStream.of. Call IntStream#boxed to use boxing conversion from int primitive to Integer objects. Collect into a list using Stream.collect( Collectors.toList() ). Or more simply in Java 16+, call Stream#toList(). Example: int[] ints = {1,2,3}; List<Integer> list = Arrays.stream(ints).boxed().collect(Collectors.toList()); … Read more