They are entirely different constructs. A HashMap is an implementation of Map. A Map maps keys to values. The key look up occurs using the hash. On the other hand, a HashSet is an implementation of Set. A Set is designed to match the mathematical model of a set. A HashSet does use a HashMap to back its implementation, as you noted. However, it implements an entirely different interface. … Read more
To reverse an int array, you swap items up until you reach the midpoint, like this: The way you are doing it, you swap each element twice, so the result is the same as the initial list.
^ in java does not mean to raise to a power. It means XOR. You can use java’s Math.pow() And you might want to consider using double instead of int—that is: Note that 199/100 evaluates to 1.
is there a possibility that casting a double created via Math.round() will still result in a truncated down number No, round() will always round your double to the correct value, and then, it will be cast to an long which will truncate any decimal places. But after rounding, there will not be any fractional parts remaining. Here are the docs from Math.round(double): … Read more
You can use the localeCompare() method.
You can use the List.addAll() method. It accepts a Collection as an argument, and your set is a Collection. EDIT: as respond to the edit of the question.It is easy to see that if you want to have a Map with Lists as values, in order to have k different values, you need to create k different lists.Thus: You cannot avoid … Read more
I would recommend making Rock, Paper and Scissors objects. The objects would have the logic of both translating to/from Strings and also “knowing” what beats what. The Java enum is perfect for this. The parseType method can return null if the String is not a valid type. And you code can check if the value is null and if … Read more
Using java.io.File:
Apart from an understanding of the accesses amongst modules and their respective packages. I believe the crux of it lies in the Module System#Relaxed-strong-encapsulation and I would just cherry-pick the relevant parts of it to try and answer the question. What defines an illegal reflective access and what circumstances trigger the warning? To aid in the migration … Read more
“Exception in thread “main” java.lang.IndexOutOfBoundsException: Index: 0, Size: 0″ is the main error I get when I compile this method: How can I fix this?