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

One of the mutual work spell 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 y'all are processing a List using Stream's map together with filter method, y'all ideally desire your trial inwards about collection thence that y'all tin top it to other component division of program. Though java.util.stream.Stream degree has toArray() method to convert Stream to Array, but  there is no similar method to convert Stream to List or Set. Java has a blueprint philosophy of providing conversion method betwixt novel together with one-time API classes e.g. when they introduced Path degree inwards JDK 7, which is similar to java.io.File, they provided a toPath() method to File class. Similarly they could conduct maintain provided convenient methods similar toList(), toSet() into Stream class, but unfortunately they conduct maintain non done that. Anyway, It seems they did thought close this together with provided a degree called Collector to collect the trial of current operations into dissimilar container or Collection classes. Here y'all volition discovery methods similar toList(), which tin live used to convert Java 8 Stream to List. You tin likewise role whatever List implementation degree e.g. ArrayList or LinkedList to acquire contents of that Stream. I would conduct maintain preferred having those method at-least the mutual ones straight into Stream but silent in that place is something y'all tin role to convert a Java 8 Stream to List. BTW, my enquiry to this business likewise reveals several other agency to hit the same result, which I conduct maintain summarized inwards this tutorial. If would propose to prefer measure way, which is past times using Stream.collect() together with Collectors class, but its practiced to know other ways, simply inwards instance if y'all need.

Java 8 Stream to List conversion - 5 examples

Here are 5 unproblematic 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 trial of current inwards a container e.g. List, Set or whatever Collection. Stream degree has a collect() method which accepts a Collector together with y'all tin role Collectors.toList() method to collect the trial inwards a List.

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

Using Collectors.toCollection() method
This is genuinely generalization of previous method, hither instead of creating List, y'all tin 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 come across 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 likewise 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 likewise sue forEach() method to become through all chemical component of Stream i past times i together with add together them into a novel List or ArrayList. This is simple, pragmatic approach, which beginners tin 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 thence elements may live processed out of guild but if y'all desire to add together them into the same guild they were nowadays inwards Stream, y'all tin role forEachOrdered() method. If y'all are non comfortable amongst forEach, I propose expect at this Stream tutorial to sympathize more.

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

Using toArray() method
Stream provides direct method to convert Stream to array, toArray(). The method which accepts no declaration returns an object array equally shown inwards our our sample program, but y'all tin silent acquire which type of array y'all desire past times using overloaded version of that method. Just similar nosotros conduct maintain done inwards next instance to do 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 plan to demonstrate all these 5 methods of converting Java 8 Streams to List. You tin straight run them if y'all conduct maintain 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 upward together with volition help y'all to acquire 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 instance : " + 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, sec 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);          // fourth 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, fourth Way : " + myList);                  // fifth agency of creating List from Stream inwards Java         // but unfortunately this creates array of Objects         // equally 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 instance of Stream to List inwards Java 8 : " + listOfNames);                   // tin nosotros convert the inwards a higher house method to String[] instead of          // Object[], yep past times using overloaded version of toArray()         // equally 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 final instance : " + listOfShapes);      }  }   Output : Java 8 Stream to List, 1st instance : [code, logic, program, review, skill] Java 8 Stream to List, sec Way : [one, two, three, four, five] Java 8 Stream to List, third Way : [abc, cde, efg, jkd, res] Java 8 Stream to List, fourth Way : [one, two, three, four, five] fifth instance of Stream to List in Java 8 : [James, Jarry, Jasmine, Janeth] modified version of last instance : [Rectangle, Square, Circle, Oval]

That's all close how to convert Stream to List inwards Java 8. You conduct maintain seen in that place are several ways to perform the conversion but I would propose y'all stick amongst measure approach i.e. past times using Stream.collect(Collectors.toList()) method.

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