Java Eight - Journeying Of For Loop Inwards Java, For(Index) To Foreach()

for loop has come upward a long way inwards Java 8 amongst novel forEach() method in java.util.stream.Stream class. In this article, nosotros volition create got a hold off at the journeying of for loop inwards dissimilar versions of Java programming language. for loop is in that place from the real offset of Java i.e. JDK 1.0. Almost all Java programmers create got used the classical for() loop, equally it is also an essential programming construct, I approximate only adjacent to if-else, but when the foreach loop or equally some people telephone band it enhanced for loop was introduced inwards JDK 1.5, everything changed from looping over Collection together with array perspective. Yesterday's pop looping cook choke erstwhile together with ugly together with to a greater extent than elegant solution took over. It was shorter, cleaner together with less mistake prone, what else yous demand at that time.

Things were quite inwards price of for loop from concluding 10 years, but  In Java 8, looping has taken some other big measuring inwards its novel avatar, forEach() method. Its non entirely short, cook clean but also create got payoff of lazy evaluation together with inwards built parallelism of Java 8 Stream. let's revisit this journeying of for loop inwards Java inwards this shipping service of .


Pre-JDK 1.5, this was my favorite way of iterating over an ArrayList or HashSet :

// pre JDK 1.5, printing each chemical cistron of List using for loop List<String> countries = Arrays.asList("India", "Australia", "England", "South Africa");          for(int i=0; i < countries.size(); i++){    System.out.println(countries.get(i)); }

So when foreach loop or advanced for loop was added on Java 5, I rapidly adopted to next vogue of looping over Collection or List :

for(String province : countries){      System.out.println(country); }

This was much shorter, cleaner together with less mistake prone than previous 1 together with everybody loved it. You don't demand to proceed rail of index, yous don't demand to telephone band size() method inwards every measuring together with it was less mistake prone than previous one, but it was however imperative. You are telling compiler what to practise together with how to practise similar traditional for loop.

Things modify drastically when the functional vogue of programming was introduced inwards Java 8 via lambda expression together with novel Stream API. Now yous tin loop over your collection without whatever loop inwards Java, yous only demand to exercise forEach() method of java.util.Stream class, equally shown below :

countries.stream().forEach(str -> System.out.println(str));

This code has reduced looping over collection or listing into only 1 line. To add together into, If yous desire to perform some pre processing chore e.g. filtering, conversion or mapping, yous tin also practise this inwards the same trace of piece of occupation equally shown below :

countries.stream()          .filter(country -> country.contains("n"))          .forEach(str -> System.out.println(str));

This code volition straight off entirely impress "India" together with "England" equally it contains the missive of the alphabet "n". Java SE 8 for Really Impatient By Cay S. Horstmann  to acquire to a greater extent than nearly filtering inwards Java 8.

This approach has several payoff over previous 2 imperative approaches, foremost it segregate what to practise from how to do. You are only telling API to filter listing based upon status yous create got given together with and thence impress those element. Now API tin impress it past times the way it wants, yous don't demand to worry about. Benefit is, yous don't demand to write imperative code, yous volition also practise goodness from lazy evaluation together with whatever functioning improvement done past times API to attain your task. You tin fifty-fifty brand your code to a greater extent than concise using method reference characteristic of Java 8, equally shown below :

countries.stream()          .filter(country -> country.contains("n"))          .forEach(System.out::println);

That "::" or orbit resolution operator of C++ is used for method reference, since yous are non doing anything amongst String declaration of println() together with thence only passing it, yous tin exercise method reference in that place to brand your code to a greater extent than cook clean together with concise.

Here is the consummate code event of using dissimilar for loops inwards Java world, including Java 8 forEach() method. This event demonstrate gradual changes made inwards for loop from Java 1.4, v together with Java 8 versions.

package test;  import java.io.IOException; import java.util.Arrays; import java.util.List;   /**  * Java Program to demonstrate dissimilar ways to loop over collection inwards   * pre Java 8 together with Java 8 the world using Stream's forEach method.  * @author Javin Paul  */ public class JourneyOfForLoopInJava {      public static void main(String args[]) throws IOException {          // pre JDK 1.5, printing each chemical cistron of List using for loop         List<String> countries = Arrays.asList("India", "Australia", "England", "South Africa");                  for(int i=0; i<countries.size(); i++){             System.out.println(countries.get(i));         }                           // In Java 5, nosotros god advanced for loop, which makes it slow to loop over         // List or Collection                 for(String province : countries){             System.out.println(country);         }                  // In Java 8, yous tin exercise forEach method of Stream bird to loop over         // whatever List or Collection         countries.stream().forEach(str -> System.out.println(str));                  // doing some pre-processing filtering on our list     // volition impress India, England equally entirely they incorporate "n"         countries.stream()                 .filter(country -> country.contains("n"))                 .forEach(str -> System.out.println(str));                  // making the code to a greater extent than concise using method reference          countries.stream()                 .filter(country -> country.contains("n"))                 .forEach(System.out::println);     }   }

So yous create got seen, for loop has come upward a long way from JDK 1 to JDK 8, peculiarly when yous exercise amongst Collection. Gone are the days, when yous demand to worry nearly looping index, initializing it properly, making certain it ends properly to avoid IndexOutOfBoundsException together with calling corresponding get() method on List. Java v was foremost measuring inwards making looping over Collection slow but Java 8 has provided a much powerful of functional vogue looping inwards Java. In fact, it's non fifty-fifty a loop its only a method call, which way yous tin write high-performance Java Collection code without using a loop.

So adjacent time, yous demand to loop over collection, only don't exercise a uncomplicated or advanced for loop, considering using forEach() method of Stream. You volition non entirely practise goodness from modern way of filtering together with mapping but also from lazy evaluation together with functioning improvement past times smart looping implementation of API itself.

Further Learning
The Complete Java MasterClass
tutorial)

How to exercise Stream bird inwards Java 8 (tutorial)

How to exercise filter() method inwards Java 8 (tutorial)

How to exercise forEach() method inwards Java 8 (example)

How to bring together String inwards Java 8 (example)

How to convert List to Map inwards Java 8 (solution)

How to exercise peek() method inwards Java 8 (example)

5 Books to Learn Java 8 from Scratch (books)

How to convert current to array inwards Java 8 (tutorial)

Java 8 Certification FAQ (guide)

Java 8 Mock Exams together with Practice Test (test)

Thanks for reading this article thence far. If yous similar this article together with thence delight portion amongst your friends together with colleagues. If yous create got whatever question, doubt, or feedback together with thence delight drib a comment together with I'll endeavour to respond your question.

P.S. : Java 8 is bundle of many exciting features similar this, if yous are interested to acquire to a greater extent than nearly them, yous tin choice whatever of the next books :

• Java 8 inwards Action: Lambdas, Streams, together with functional-style programming (see here)
• Mastering Lambdas: Java Programming inwards a Multicore World (see here)

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