JAVA EE: Java Tutorial: Lambda expression in java | Java Lambda expressions[forEach method of List]

Tuesday 30 May 2017

Java Tutorial: Lambda expression in java | Java Lambda expressions[forEach method of List]

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Java Tutorial: Lambda expression in java | Java Lambda expressions[forEach method of List]

LambdaDemo1.java

import java.util.ArrayList;
import java.util.List;

public class LambdaDemo1
{

    public static void main(String[] args)
    {

        List<String> nameList = new ArrayList<>();
        nameList.add("Peter");
        nameList.add("John");
        nameList.add("Juli");
        nameList.add("Stephan");

        /*
         * Before Java 8, Normal way to loop a list.
         */
        for (String name : nameList)
        {
            System.out.println(name);
        }

        System.out.println("------------------------------------");

        /*
         * In Java 8, we can loop a List with forEach + lambda
         * expression or method reference.
         */
        nameList.forEach(name -> System.out.println(name));

    }

}

Output

Peter
John
Juli
Stephan
------------------------------------
Peter
John
Juli
Stephan

LambdaDemo2.java

import java.util.ArrayList;
import java.util.List;

public class LambdaDemo2
{

    public static void main(String[] args)
    {

        List<String> nameList = new ArrayList<>();
        nameList.add("Peter");
        nameList.add("John");
        nameList.add("Juli");
        nameList.add("Stephan");

        /*
         * In Java 8, we can loop a List with forEach + lambda
         * expression or method reference.
         */

        nameList.forEach(name -> {
            if ("John".equals(name))
            {
                System.out.println("Hello " + name);
            }
        });
    }

}

Output

Hello John

LambdaDemo3.java

import java.util.ArrayList;
import java.util.List;

public class LambdaDemo3
{

    public static void main(String[] args)
    {

        List<String> nameList = new ArrayList<>();
        nameList.add("Peter");
        nameList.add("John");
        nameList.add("Juli");
        nameList.add("Stephan");

        /*
         * In Java 8, we can loop a List with forEach + lambda
         * expression or method reference.
         */

        //method reference
        nameList.forEach(System.out::println);
    }

}

Output

Peter
John
Juli
Stephan

LambdaDemo4.java

import java.util.ArrayList;
import java.util.List;

public class LambdaDemo4
{

    public static void main(String[] args)
    {

        List<String> nameList = new ArrayList<>();
        nameList.add("Peter");
        nameList.add("John");
        nameList.add("Juli");
        nameList.add("Stephan");

        /*
         * In Java 8, we can loop a List with forEach + lambda
         * expression or method reference.
         */

        //Stream and filter
        nameList.stream()
            .filter(name->name.contains("Juli"))
            .forEach(System.out::println);
    }

}