Java important pro

Filter and then find the first or return the default value

import java.util.Arrays;

import java.util.List;

           public class Main 

           {

  public static void main(String[] args) 

  {

     List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5);

     int i = numbers.stream().filter(n -> n % 2 == 0).findFirst().orElse(-1);

               System.out.println(i);

   }

}

Filter even number                       

import java.util.Arrays;

import java.util.List;

           public class Main 

{

 public static void main(String[] args) 

{

     List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5);

     numbers.stream().filter(n -> n % 2 == 0).forEach(System.out::println);

   }

          }

Filter number list and get even numbers

import java.util.Arrays;

import java.util.List;

public class Main 

{

           public static void main(String[] args) 

           {

    List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);

    numbers.stream()

           .filter(value -> value % 2 == 0)

           .forEach(System.out::println);

  }

}

Filter twice

import java.util.Arrays;

import java.util.List;

import java.util.Objects;

public class Main 

{

            public static void main(String[] args)  

           {

    List liste = Arrays.asList("Xml", "Html", "Css", null);

               liste.parallelStream()

            .filter(e -> (!Objects.equals(e, null))) 

            .filter(e -> (e.length() > 3)) 

            .forEach(e -> 

            {  

                System.out.println("Bigger length than 3 in List: " + e);

            });

                }

}

Find first matched item

import java.util.Arrays;

import java.util.List;

import java.util.Optional;

public class Main 

{

           public static void main(String[] args) 

           {

    List names = Arrays.asList("XML", "HTML", "Java", "Javascript", "CSS", "Static");

           Optional firstS = names.stream().filter(name ->  name.startsWith("S")).findFirst();

    System.out.println(firstS.orElse("None found"));

  }

}

Output default if not found

import java.util.Arrays;

import java.util.List;

import java.util.Optional;

public class Main 

{

           public static void main(String[] args) 

           {

    List names = Arrays.asList("XML", "HTML", "Java", "Javascript", "CSS", "Static");

    Optional firstS = names.stream().filter(name -> name.startsWith("S")).findFirst();

    System.out.println(firstS.orElse("None found"));

  }

}