Look at computeIfPresent, computeIfAbsent methods. (map.get("B")) // prints "b - new"Ĭonditional computes are also available. Now you can directly modify with help of compute method. Gone are the days when you needed to get the value for specific keys, process it and put them back. Do not override keys accidentally use putIfAbsentĪs the method name is self explanatory, here is an example. In the same way you can use replace, remove methods to check by key and values pairs together. Map.replaceAll((k, v) -> "x") // values is "x" for all keys.Īnd replace(K key, V oldValue, V newValue) method replaces the entry for the specified key only if currently mapped to the specified value. replaceAll Can replace all the values in a single attempt Map map = new HashMap()
New utility default methods have been added now. String val = map.getOrDefault("B", "Nah!") This method returns the value to which the specified key is mapped, otherwise returns the given defaultValue if this map contains no mapping for the key.
#JAVA MERGE METHOD MAP CODE#
Legacy code for checking containsKey got moved to default method getOrDefault. Get rid off ugly if-else condition, use getOrDefault method. Now it is super easy to iterate over map just like List. We all know how ugly is the old fashioned way of iterating and finally implementers added a default method forEach. This is very revealing feature so far in Map. If you observe the above example code, while printing I used the method forEach method. SortedByKey.forEach(System.out::println) List> sortedByKey = map.entrySet().stream().sorted(()) Now Map interface added default methods which gives you comparators for different styles like comparingByKey, comparingByValue. Sorting Map directly with Comparators.Īs we know Map is in order, it is a lot of struggle to get it sorted. A lot of internal architecture/performance changes been happend but I am just going to discuss about the useful methods been added. Since there are a lot of changes,let us see the changes happened to Map first. So I decided to explore the Collections framework changes one by one. Looking at open source projects on GitHub and some enterprise project codes which built on Java8, I rarely see new methods of Collections framework being used and people mostly using the old school methods. On the other hand, the native Collection API also got improved and added few useful and powerful features. However I recently came across an article saying that most using feature of Java8 is streams which are on Demand Collections. Java programmers around the world started using it already in their new projects. It is been a quite a long time ever since Java8 released.
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