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How can we implement methods of Stream API in Java 9?
Stream API provides lots of built-in functionality to help in performing operations on a collection using a stream pipeline. The API is declarative programming that makes the code precise and less error-prone. In Java 9, few useful methods have added to Stream API.
- Stream.iterate(): This method can be been used as stream version replacement for traditional for-loops.
- Stream.takeWhile(): This method can be used in a while loop that takes value while the condition is met.
- Stream.dropWhile(): This method can be used in a while loop that drops value while the condition is met.
In the below example, we can implement the static methods: iterate(), takeWhile(), and dropWhile() methods of Stream API.
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].startsWith("R")) {
System.out.println(i);
}
}
System.out.println("[Stream.iterate] Indexes of names starting with R = ");
Stream.iterate(0, i -> i < sortedNames.length, i -> ++i).filter(i -> sortedNames[i].startsWith("R")).forEach(System.out::println);
String namesAtoC = Arrays.stream(sortedNames).takeWhile(n -> n.charAt(0) <= 'C')
.collect(Collectors.joining(","));
String namesDtoZ = Arrays.stream(sortedNames).dropWhile(n -> n.charAt(0) <= 'C')
.collect(Collectors.joining(","));
System.out.println("Names A to C = " + namesAtoC);
System.out.println("Names D to Z = " + namesDtoZ);
}
}Output
[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
Updated on: 15-Apr-2020
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