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Tag: list

Intersection and union of ArrayLists in Java

Are there any methods to do so? I was looking but couldn’t find any. Another question: I need these methods so I can filter files. Some are AND filters and some are OR filters (like in set theory), so I need to filter according to all files and the unite/intersects ArrayLists that holds those files. Should I use a different

Print array without brackets and commas

I’m porting a Hangman game to Android and have met a few problems. The original Java program used the console, so now I have to somehow beautify the output so that it fits my Android layout. How do I print an array without the brackets and commas? The array contains slashes and gets replaced one-by-one when the correct letter is

When to use a Map instead of a List in Java?

I didn’t get the sense of Maps in Java. When is it recommended to use a Map instead of a List? Answer Java map: An object that maps keys to values. A map cannot contain duplicate keys; each key can map to at most one value. Java list: An ordered collection (also known as a sequence). The user of this

Java: convert List to a join()d String

JavaScript has Array.join() Does Java have anything like this? I know I can cobble something up myself with StringBuilder: .. but there’s no point in doing this if something like it is already part of the JDK. Answer String.join With Java 8 you can do this without any third party library. If you want to join a Collection of Strings

Why is list.size()>0 slower than list.isEmpty() in Java?

Why is list.size()>0 slower than list.isEmpty() in Java? On other words why isEmpty() is preferable over size()>0? When I look at the implementation in ArrayList, then it looks like the speed should be the same: ArrayList.size() ArrayList.isEmpty() If we just write a simple program to get the time take by both the methods, that case size() will take more isEmpty()

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