JAVA EE: How to filter the List of Names using Java 8 Stream | Java 8 streams tutorial

Tuesday 4 July 2017

How to filter the List of Names using Java 8 Stream | Java 8 streams tutorial | Streams in Java 8

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How to filter the List of Names using Java 8 Stream | Java 8 streams tutorial | Streams in Java 8

FilterDemo.java

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

public class FilterDemo
{
    public static void main(String[] args)
    {
        List<String> namesList = Arrays.asList("Ram", "Peter","Pradeep", "Steve");

        List<String> filteredNameList = getFilterOutput(namesList, "P");
        for (String name : filteredNameList)
        {
            System.out.println(name); 
        }
    }

    private static List<String> getFilterOutput(List<String> namesList, String filter)
    {
        List<String> filteredNameList = new ArrayList<>();
        for (String name : namesList)
        {
            if (name.startsWith("P"))
            {
                filteredNameList.add(name);
            }
        }
        return filteredNameList;
    }
}

Output

Peter
Pradeep

StreamDemo1.java

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

public class StreamDemo1
{
    public static void main(String[] args)
    {
        List<String> namesList = Arrays.asList("Ram", "Peter","Pradeep", "Steve");

        /*
         * Convert list to stream.
         * 
         * Returns a sequential Stream with this collection as its
         * source.
         */
        Stream<String> stream = namesList.stream();
        /*
         * filters the name, starts with "P".
         * 
         * Returns a stream consisting of the elements of this stream
         * that match the given predicate.
         */
        stream = stream.filter(name -> name.startsWith("P"));

        /*
         * Collect the output and convert streams to a List.
         * 
         * Performs a mutable reduction operation on the elements of
         * this stream using a Collector.
         */
        List<String> filteredNameList = stream.collect(Collectors.toList());

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

}

Output

Peter
Pradeep

StreamDemo2.java

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

public class StreamDemo2
{
    public static void main(String[] args)
    {
        List<String> namesList = Arrays.asList("Ram", "Peter","Pradeep", "Steve");

        
        List<String> filteredNameList = namesList.stream() //convert list to stream
                .filter(name -> name.startsWith("P")) //filters the name, starts with "P".
                .collect(Collectors.toList()); //collect the output and convert streams to a List
        

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

}