Let’s see example of flatMap. This method is part of the Stream API. We can use when we have nested collections but need only one level (we need to remove the nested collections ) and merge all the elements in one single collection. Lets have a simple class Main: The result is:
Let’s see how to use map grouping by functionality with Java stream. We have GenericRecord class that hold the data of the person and also the addresses of the people. In many cases we want to split this information to Peron and Addresses and we want to remove the duplicate information. See how several time … Read more
In this example we will make Java program that filter List with Predicate. is create with positive and negative numbers. Then this list is filter by Stream.filter method which accept predicate as argument. There are three examples: Output:
Program that convert from Map to List in several ways. There are several cases based on the desired result: Output:
Example of a Java program which convert Set to List with ArrayList’s constructor which accept Collection. Output:
This is example of java program we will see ho to convert list to set. We use List to keep order of the element which are added. On the other hand Java Set does not keep the elements in order and also does not keep duplicate elements. Our program let’s created duplicated elements and add … Read more
If you need to get only the elements which are common for two sets you can use the method retainAll. The documentation for this method states: “Method signature: boolean retainAll(Collection<?> c) Description: Retains only the elements in this set that are contained in the specified collection (optional operation). In other words, removes from this set all … Read more
Here are 3 ways to find the maximum number inside a list with lambda in Java:
There is a very important method indexOf which is part of the List interface. The description in Java documentation states: “Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element. More formally, returns the lowest index i such that (o==null ? get(i)==null : o.equals(get(i))), or … Read more
