into method in the Stream class

[Quazi Irfan]

I am learning the use of stream API on Java collections by following this blog: http://java.amitph.com/2012/10/java-collections-api-enhancements.html

I've stumbled upon this piece of code that I can't seem to get to work,

List<Student> studentsNamedAsTom =
           students.filter (student -> student.getName.equals("Tom"))
           .into (new ArrayList<>());

I am trying to reproduce the behavior with the following code,

import java.util.ArrayList;

public class FeatureTest
{
    public static void main(String[] args) 
    {
        ArrayList<String> list = new ArrayList<>();
        list.add("a");
        list.add("b");
        list.add("c");

        ArrayList<String> filteredList = list.stream().filter(name -> name.equals("a")).into(new ArrayList<>()); 
    }
}

But, IntellijIDEA says that it can not resolve method 'into'. I looked into Sream class, and I could not find a method named 'into'.

So, how do I make the code work? The blog is from 2012 - did the API change?

[Carey Brown]

I've never see "into" before. You can use .collect() with a toList() Collector. Note that you should use "List" instead of "ArrayList". You can find the documentation for Collectors HERE.

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

public class Java8Try
{
	public static void main( String[] args )
	{
		// use "List"
        List<String> list = new ArrayList<>();
        list.add("a");
        list.add("b");
        list.add("c");
 
		// use "List"
        List<String> filteredList = list.stream()
        	.filter( name -> name.equals("a") )
        	.collect( Collectors.toList() );
        
        System.out.println( filteredList );
 	}
}

[Quazi Irfan]

Thank you!

[Prasad Saya]

ArrayList<String> list = new ArrayList<>();
       list.add("a");
       list.add("b");
       list.add("c");
       ArrayList<String> filteredList = list.stream().filter(name -> name.equals("a")).into(new ArrayList<>());
   }
}

But, IntellijIDEA says that it can not resolve method 'into'. I looked into Sream class, and I could not find a method named 'into'.

As I see there is no into method in the java.util.stream.Stream. That's the reason the IDE is complaining.  The correct way to do the reduction operation (writing the result to a List collection) is:

List<String> filteredList = list.stream()
								.filter(name -> name.equals("a"))
								.collect(Collectors.toList());

[Piet Souris]

If you do want an ArrayList, it can be done with this:

ArrayList<String> filteredList = list.stream()
         .filter( name -> name.equals("a") )
         .collect( Collectors.toCollection(ArrayList::new) );

[Campbell Ritchie]

Quazi Irfan wrote:. . . following this blog: . . . The blog is from 2012 - did the API change?

That tutorial isn't very helpful, even to people who can actually read the white text on dark grey

That link wrote:. . . . The upcoming additions to the Java 8’s Collections API will make it to support Internal Iterations. . . .

It appears to have been written before Java8 became available, and was predicting changes which were not actually implemented. The into() method doesn't exist; as Prayad Saya said. You would have to use collect(...)