How can we implement methods of Stream API in Java 9?

StreamAPI provides a number of built-in functions to aid in working with stream pipes. The API is declarative programming, making the code more precise and less error-prone. In Java 9, some useful methods were added to the Stream API.

• Stream.iterate(): This method can be used as an alternative to the stream version of the traditional for loop.
• Stream.takeWhile(): This method can be used in a while loop to take the value when the condition is met.
• Stream.dropWhile(): This method can delete the value in the while loop when the condition is met.

In the following example, we can implement static methods: iterate(), takeWhile( ), and dropWhile( of Stream API ) method.

Example

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

public class StreamAPITest {
   public static void main(String args[]) {
      String[] sortedNames = {"Adithya", "Bharath", "Charan", "Dinesh", "Raja", "Ravi", "Zaheer"};

      System.out.println("[Traditional for loop] Indexes of names starting with R = ");
      for(int i = 0; i < sortedNames.length; i++) {
         if(sortedNames[i].<strong>startsWith</strong>("R")) {
            System.out.println(i);
         }
      }
      System.out.println("[Stream.iterate] Indexes of names starting with R = ");
      <strong>Stream.iterate</strong>(0, i -> i < sortedNames.length, i -> ++i).<strong>filter</strong>(i -> sortedNames[i].startsWith("R")).<strong>forEach</strong>(System.out::println);

      String namesAtoC = <strong>Arrays.stream</strong>(sortedNames).<strong>takeWhile</strong>(n -> n.<strong>charAt</strong>(0) <= &#39;C&#39;)
.<strong>collect</strong>(Collectors.joining(","));

      String namesDtoZ = <strong>Arrays.stream</strong>(sortedNames).<strong>dropWhile</strong>(n -> n.charAt(0) <= &#39;C&#39;)
.<strong>collect</strong>(Collectors.joining(","));

      System.out.println("Names A to C = " + namesAtoC);
      System.out.println("Names D to Z = " + namesDtoZ);
   }
}

Output

<strong>[Traditional for loop] Indexes of names starting with R =
4
5
[Stream.iterate] Indexes of names starting with R =
4
5
Names A to C = Adithya,Bharath,Charan
Names D to Z = Dinesh,Raja,Ravi,Zaheer</strong>

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