In Java, if we remove items from a List while iterating it, it will throw java.util.ConcurrentModificationException. This article shows a few ways to solve it. Table of contents 1. java.util.ConcurrentModificationException 2. Java 8 Collection#removeIf 2.1 removeIf examples 2.2 removeIf uses Iterator 3. ListIterator example 4. Filter and Collect example 5. References P.S Tested with Java …
This article shows a few ways to get keys from value in HashMap. 1. HashMap can contain null for key and value 2. Get all keys from HashMap – keySet() 3. Get keys from value in HashMap 4. Get keys from value in HashMap (Java 8 Stream) 5. HashMap only has one item 6. References …
This article shows different ways to initialize HashMap in Java. Initialize a HashMap (Standard) Collections.singletonMap Java 9 Map.of Java 9 Map.ofEntries Create a function to return a Map Static Initializer Java 8, Stream of SimpleEntry Conclusion After initialized a HashMap, the result is either a mutable map or an immutable map: Mutable map – It …