In Java 8 remove selected item from Collection? It can be done in at least two ways both of which we are going to implement here. Let’s code!

Very common task is creation of Map from a List of objects. In this post we show how to use Java 8 to convert List to Map using Collectors.

In this article we present Java 8 forEach on examples. These are very convenient methods for use with Lambda Expressions and method references.

java.util.Map.merge(key, value, BiFunction) The method Map.merge(key, value, BiFunction) associates given value with the given key or calculates the new value from the old value and the given one using provided remapping function.

java.util.Map.getOrDefault(key, defaultValue) The method Map.getOrDefault(key, defaultValue) returns mapped value for the given key or defaultValue if there is no such mapping.

java.util.Map.forEach(BiConsumer) The method Map.forEach(BiConsumer) performs the given action for each entry of the map until all are processed or exception is thrown.

java.util.Map.computeIfPresent(Key, BiFunction) The method Map.computeIfPresent(Key, BiFunction) computes a new mapping for the given key and its current mapping value if the value exists and is not null.

java.util.Map.computeIfAbsent(key, Function) The method Map.computeIfAbsent(key, Function) computes the new value and associates it with the key if there is no mapping for the given key or the mapping is null. Returns the new value associated with the key.