5 Ways To Convert Coffee Eight Stream To Listing - Example, Tutorial

One of the mutual work piece working amongst Stream API inwards Java 8 is how to convert a Stream to List inwards Java because in that place is no toList() method nowadays inwards Stream class. When you lot are processing a List using Stream's map together with filter method, you lot ideally desire your upshot inwards roughly collection thence that you lot tin sack overstep it to other component of program. Though java.util.stream.Stream shape has toArray() method to convert Stream to Array, but  there is no similar method to convert Stream to List or Set. Java has a pattern philosophy of providing conversion method betwixt novel together with former API classes e.g. when they introduced Path shape inwards JDK 7, which is similar to java.io.File, they provided a toPath() method to File class. Similarly they could receive got provided convenient methods similar toList(), toSet() into Stream class, but unfortunately they receive got non done that. Anyway, It seems they did thought most this together with provided a shape called Collector to collect the upshot of current operations into dissimilar container or Collection classes. Here you lot volition detect methods similar toList(), which tin sack live used to convert Java 8 Stream to List. You tin sack every bit good role whatever List implementation shape e.g. ArrayList or LinkedList to acquire contents of that Stream. I would receive got preferred having those method at-least the mutual ones straight into Stream but even thence in that place is something you lot tin sack role to convert a Java 8 Stream to List. BTW, my inquiry to this draw of piece of work every bit good reveals several other agency to accomplish the same result, which I receive got summarized inwards this tutorial. If would advise to prefer measure way, which is past times using Stream.collect() together with Collectors class, but its skillful to know other ways, merely inwards instance if you lot need.

Java 8 Stream to List conversion - 5 examples

Here are 5 elementary ways to convert a Stream inwards Java 8 to List e.g. converting a Stream of String to a List of String, or converting a Stream of Integer to List of Integer together with thence on.

Using Collectors.toList() method
This is the measure agency to collect the upshot of current inwards a container e.g. List, Set or whatever Collection. Stream shape has a collect() method which accepts a Collector together with you lot tin sack role Collectors.toList() method to collect the upshot inwards a List.

List listOfStream = streamOfString.collect(Collectors.toList());

Using Collectors.toCollection() method
This is truly generalization of previous method, hither instead of creating List, you lot tin sack collect elements of Stream inwards whatever Collection, including ArrayList, LinkedList or whatever other List. In this example, nosotros are collecting Stream elements into ArrayList.  The toColection() method returns a Collector that accumulates the input elements into a novel Collection, inwards run into order. The Collection is created past times the provided Supplier instance, inwards this instance nosotros are using ArrayList::new, a constructor reference to collect them into ArrayList. You tin sack every bit good role lambda aspect inwards house of method reference here, but method reference results inwards much to a greater extent than readable together with concise code.

List listOfString  = streamOfString.collect(Collectors.toCollection(ArrayList::new));

Using forEach() method
You tin sack every bit good sue forEach() method to become through all chemical factor of Stream 1 past times 1 together with add together them into a novel List or ArrayList. This is simple, pragmatic approach, which beginners tin sack role to learn.

Stream streamOfLetters = Stream.of("abc", "cde",                 "efg", "jkd", "res"); ArrayList listing = new ArrayList<>(); streamOfLetters.forEach(list::add);

Using forEachOrdered method
This is extension of previous example, if Stream is parallel together with thence elements may live processed out of fellowship but if you lot desire to add together them into the same fellowship they were nowadays inwards Stream, you lot tin sack role forEachOrdered() method. If you lot are non comfortable amongst forEach, I advise await at this Stream tutorial to sympathise more.

Stream streamOfNumbers = Stream.of("one", "two",                 "three", "four", "five"); ArrayList myList = new ArrayList<>(); streamOfNumbers.parallel().forEachOrdered(myList::add);

Using toArray() method
Stream provides take away method to convert Stream to array, toArray(). The method which accepts no declaration returns an object array every bit shown inwards our our sample program, but you lot tin sack soundless acquire which type of array you lot desire past times using overloaded version of that method. Just similar nosotros receive got done inwards next representative to exercise String array :

Stream streamOfShapes = Stream.of("Rectangle", "Square", "Circle", "Oval"); String[] arrayOfShapes = streamOfShapes.toArray(String[]::new); List listOfShapes = Arrays.asList(arrayOfShapes);

Sample Program to convert Stream to List inwards Java 8

Here is the consummate Java programme to demonstrate all these v methods of converting Java 8 Streams to List. You tin sack straight run them if you lot receive got installed JDK 8 inwards your machine. BTW, You should live using Netbeans amongst JDK 8 to code, compile together with run Java program. The IDE has got first-class back upwards together with volition assistance you lot to larn Java 8 quickly.

package test;  import java.io.IOException; import java.util.ArrayList; import java.util.Arrays; import java.util.List; import java.util.stream.Collectors; import java.util.stream.Stream;  /**  * Java Program to convert Stream to List inwards Java 8  *  * @author Javin Paul  */ public class Java8StreamToList{      public static void main(String args[]) throws IOException {         Stream<String> streamOfString = Stream.of("Java", "C++",                 "JavaScript", "Scala", "Python");          // converting Stream to List using Collectors.toList() method         streamOfString = Stream.of("code", "logic",                 "program", "review", "skill");         List<String> listOfStream = streamOfString.collect(Collectors.toList());         System.out.println("Java 8 Stream to List, 1st representative : " + listOfStream);          // Java 8 Stream to ArrayList using Collectors.toCollection method         streamOfString = Stream.of("one", "two",                 "three", "four", "five");         listOfStream = streamOfString.collect(Collectors.toCollection(ArrayList::new));         System.out.println("Java 8 Stream to List, 2d Way : " + listOfStream);          // third agency to convert Stream to List inwards Java 8         streamOfString = Stream.of("abc", "cde",                 "efg", "jkd", "res");         ArrayList<String> list = new ArrayList<>();         streamOfString.forEach(list::add);         System.out.println("Java 8 Stream to List, third Way : " + list);          // quaternary agency to convert Parallel Stream to List         streamOfString = Stream.of("one", "two",                 "three", "four", "five");         ArrayList<String> myList = new ArrayList<>();         streamOfString.parallel().forEachOrdered(myList::add);         System.out.println("Java 8 Stream to List, quaternary Way : " + myList);                  // fifth agency of creating List from Stream inwards Java         // but unfortunately this creates array of Objects         // every bit opposed to array of String         Stream<String> streamOfNames = Stream.of("James", "Jarry", "Jasmine", "Janeth");         Object[] arrayOfString = streamOfNames.toArray();         List<Object> listOfNames = Arrays.asList(arrayOfString);         System.out.println("5th representative of Stream to List inwards Java 8 : " + listOfNames);                   // tin sack nosotros convert the higher upwards method to String[] instead of          // Object[], aye past times using overloaded version of toArray()         // every bit shown below :         Stream<String> streamOfShapes = Stream.of("Rectangle", "Square", "Circle", "Oval");         String[] arrayOfShapes = streamOfShapes.toArray(String[]::new);         List<String> listOfShapes = Arrays.asList(arrayOfShapes);         System.out.println("modified version of end representative : " + listOfShapes);      }  }   Output : Java 8 Stream to List, 1st representative : [code, logic, program, review, skill] Java 8 Stream to List, 2d Way : [one, two, three, four, five] Java 8 Stream to List, third Way : [abc, cde, efg, jkd, res] Java 8 Stream to List, quaternary Way : [one, two, three, four, five] fifth representative of Stream to List in Java 8 : [James, Jarry, Jasmine, Janeth] modified version of last representative : [Rectangle, Square, Circle, Oval]

That's all most how to convert Stream to List inwards Java 8. You receive got seen in that place are several ways to perform the conversion but I would advise you lot stick amongst measure approach i.e. past times using Stream.collect(Collectors.toList()) method.

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