Knowledge Factory

The map() function is a method in the Stream class that represents a functional programming concept. In simple words, the map() is utilized to transform one object into another by applying a function. Example 1: Stream map() function with the operation of converting uppercase to lowercase. import java.util. *; import java.util.stream.Collectors ; /*Stream map() function with operation of converting uppercase to lowercase. */ public class DriverClass { public static void main ( String [] args) { List < String > list = Arrays . asList ( "SAW" , "NUN" , "JOKER" , "REVENANT" , "CAST AWAY" ); List < String > result = list .stream(). map( String ::toLowerCase). collect( Collectors . toList ()); System . out .println( result ); } } Example 2: Java program to convert List of String to List of Integers import java.util. *; i

Example 1: Counting Empty String import java.util. *; import java.util.stream.Collectors ; /*Counting Empty String*/ public class DriverClass { public static void main ( String [] args) { List < String > list = Arrays . asList ( "ss" , "" , "ss" , "" , "" ); long count = list .stream().filter(o -> o.isEmpty()).count(); System . out .println( count ); } } Example 2: Count number of String which ends with "d" import java.util. *; /*Count number of String which ends with "d"*/ public class DriverClass { public static void main ( String [] args) { List < String > list = Arrays . asList ( "method" , "static" , "void" , "abstract" , "ping" ); long count = list .stream().filter(x -> x.endsWith( "d" )).count(); System . out .println( count ); } }

In this section, we will learn how to filter a Map using the Stream filter() method. Example 1: Filter Map by Keys import java.util.HashMap; import java.util.Map; import java.util.stream.Collectors; /*Filter Map by Keys*/ public class DriverClass { public static void main( String [] args) { Map < Integer , String > hMap = new HashMap < Integer , String >(); hMap.put( 123 , "Jessie" ); hMap.put( 234 , "Alpha" ); hMap.put( 345 , "Beta" ); hMap.put( 456 , "Tesla" ); hMap.put( 111 , "Tera" ); Map < Integer , String > output = hMap.entrySet() .stream() .filter(map -> map.getKey().intValue() <= 254 ) .collect(Collectors.toMap(map -> map.getKey(), map -> map.getValue())); System.out.println( "Output: " + output); } } Output:  Example 2: Filter Map by Va

In this section, we will learn how to develop a  web application that is a basic User Management Application using MongoDB, React.js, Python, and Flask.  GitHub repository link is provided at the end of this tutorial. You can download the source code. We’re gonna build the application with the following components: After completing this tutorial what we will build? We will build a full-stack web application that is a basic User Management Application with CRUD features:     • Create User     • List User     • Update User     • Delete User     • View User Following is the screenshot of our application - -View all Users: -Add a User: -Update User: -View User We divided this tutorial into two parts.   PART 1 - Rest APIs Development using Python and Flask PART 2 - UI development using React.js     PART 1 - Rest APIs Development using Python and Flask These are APIs that Python Flask App will export:  GET all User's        :     /api/v1/users GET User by ID     :     /api/v1/users/{_id}