Jav Streams

Java Streams API. It allows you to drive away from Imperative Approach to Declarative Approach Programming.

Java Streams

Filter Methods:

• We Call the actual collection that we need
• .stream() - this takes you to abstraction
• You Can ask what you want of that list
• We have .filter() method
• We have to collect the result in the brand new list
• We used the .collect() method
• It takes Collector.toList()

			
					import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class Main {

    public static void main(String[] args) {

        List < String > lines = Arrays.asList("Adam", "Olivia", "Amelia", "Harry");

        List < String > result = lines.stream()
            .filter(line - > !"Harry".equals(line))
            .collect(Collectors.toList());

        result.forEach(System.out::println);
    }
}

			
	

			
	
			

		
	

The Above code returns

			
					  Adam, Olivia, Amelia

			
	

			
	
			

		
	

Sort Methods

• Whenever we use the Declarative approach, we need to do abstraction mode
• .stream() - this takes you to abstraction
• We have .sorted() method
• It takes Comparator.comparing() Comparator Method
• It takes Comparator.reverseOrder() Reversing Method
• We have to collect the result in the brand new list
• We used the .collect() method
• It takes Collector.toList()
• If you want to reverse the output.Just add .reversed() method

			
					import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;

public class Main {

    public static void main(String[] args) {

        List < String > list = Arrays.asList("A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O");

        List < String > sortedList = list.stream()
            .sorted(Comparator.reverseOrder())
            .collect(Collectors.toList());

        sortedList.forEach(System.out::println);
    }
}

			
	

			
	
			

		
	

It returns the output in reverse order

			
					O
N
M
L
K
J
I
H
G
F
E
D
C
B
A

			
	

			
	
			

		
	

• Streams Api Easy to work with Collections
• It tunes the performance as well
• It's Better with a large amount of data
• It reduced the many lines of codes