Iterate an Array Using Java 8 Stream API | Interview Coding Questions

May 10, 2026

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Iterate an Array Using Java 8 Stream API | Interview Coding Questions

package org.practice.basicprgms;

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;

public class IterateArrayUsingJavaStream {

	public static void main(String[] args) {
		int[] numbers = {10, 20, 50, 30, 40};		
		String[] names = {"Java", "Spring", "Microservices", "Docker"};
		
		// 1. Using Arrays.stream() + forEach()
		System.out.println("============1. Using Arrays.stream() + forEach()===========================");	
		Arrays.stream(numbers)
				.forEach(System.out::println);
		Arrays.stream(names)
				.forEach(System.out::println);
			
		// 2. Using Lambda Expression
		System.out.println("=============2. Using Lambda Expression==========================");
		Arrays.stream(numbers)
				.forEach(n -> System.out.println(n));
		Arrays.stream(names)
				.forEach(s -> System.out.println(s));
		
		
		// 3. Using IntStream.of() / Stream.of()
		System.out.println("=============3. Using IntStream.of() / Stream.of()==========================");
		IntStream.of(numbers)
				.forEach(System.out::println);
		Stream.of(names)
				.forEach(System.out::println);
		
		// 4. Convert to List Then Iterate
		System.out.println("=============4. Convert to List Then Iterate==========================");
		List<Integer> intList = 
				Arrays.stream(numbers)
					.boxed()
					.collect(Collectors.toList());
		intList.forEach(System.out::println);
		
		List<String> strList =
				Arrays.stream(names)
						.collect(Collectors.toList());
		strList.forEach(System.out::println);
		
		// 5. Using map() Before Iteration
		System.out.println("==============5. Using map() Before Iteration=========================");
		Arrays.stream(numbers)
				.map(n -> n * n)
				.forEach(System.out::println);
		
		Arrays.stream(names)
				.map(String::toUpperCase)
				.forEach(System.out::println);
		
		
		// 6. Using filter() Before Iteration
		System.out.println("==============6. Using filter() Before Iteration=========================");
		Arrays.stream(numbers)
				.filter(n -> n % 2 == 0 && n > 25)
				.forEach(System.out::println);
		
		Arrays.stream(names)
				.filter(s -> s.startsWith("M"))
				.forEach(System.out::println);		
		
		// 7. Using sorted()
		System.out.println("==============7. Using sorted()=========================");
		Arrays.stream(numbers)
				.sorted()
				.forEach(System.out::println);
		
		Arrays.stream(names)
				.sorted()
				.forEach(System.out::println);		
	}
}

output:
============1. Using Arrays.stream() + forEach()===========================
10
20
50
30
40
Java
Spring
Microservices
Docker
=============2. Using Lambda Expression==========================
10
20
50
30
40
Java
Spring
Microservices
Docker
=============3. Using IntStream.of() / Stream.of()==========================
10
20
50
30
40
Java
Spring
Microservices
Docker
=============4. Convert to List Then Iterate==========================
10
20
50
30
40
Java
Spring
Microservices
Docker
==============5. Using map() Before Iteration=========================
100
400
2500
900
1600
JAVA
SPRING
MICROSERVICES
DOCKER
==============6. Using filter() Before Iteration=========================
50
30
40
Microservices
==============7. Using sorted()=========================
10
20
30
40
50
Docker
Java
Microservices
Spring