Category: React • Beginner
Published on 15 Feb 2026
Explanation
What is Java 8 Stream? Java 8 Stream is used to process collections of data (List, Set, Map, etc.) in a functional way. It helps to: •Filter data •Sort data •Convert data •Iterate data •Collect results without writing complex loops.
Code Example
Basic Syntax
collection.stream()
.operation()
.operation()
.operation();
Example:
list.stream()
.filter()
.map()
.collect();
Explanation
Java 8 Stream with List #white-Create List: #white-Description: •stream() → convert list to stream •forEach() → print values
Code Example
import java.util.*;
import java.util.stream.*;
public class Test {
public static void main(String[] args) {
List<String> list = Arrays.asList("Ram",
"John", "Sam", "David");
list.stream()
.forEach(System.out::println);
}
}
Explanation
Filter List #white-Filter names starting with "J"
Code Example
List<String> list = Arrays.asList("Ram", "John", "Sam", "Jack");
list.stream()
.filter(name -> name.startsWith("J"))
.forEach(System.out::println);
Output:
John
Jack
Description:
filter() → filters data based on condition
Explanation
Convert List (map)
Code Example
Convert to uppercase
List<String> list = Arrays.asList("Ram",
"John");
list.stream()
.map(name -> name.toUpperCase())
.forEach(System.out::println);
Output:
RAM
JOHN
Description:
map() → transforms data
Explanation
Collect result into List
Code Example
List<String> list = Arrays.asList("Ram", "John", "Sam");
List<String> result =
list.stream()
.filter(name -> name.startsWith("S"))
.collect(Collectors.toList());
System.out.println(result);
Output:
[Sam]
Description:
collect() → store result
Explanation
#white-Stream with Map: #white-Map has: •key •value #white-Use: map.entrySet().stream()
Code Example
Map<Integer, String> map = new HashMap<>(); map.put(1, "Ram"); map.put(2, "John"); map.put(3, "Sam"); map.entrySet() .stream() .forEach(entry -> System.out.println(entry.getKey() + " " + entry.getValue())); Output: 1 Ram 2 John 3 Sam Description: entrySet() → get key and value
Explanation
Filter Map
Code Example
map.entrySet()
.stream()
.filter(entry -> entry.getValue().startsWith("J"))
.forEach(entry ->
System.out.println(entry.getValue()));
Output:
John
Explanation
Convert Map values to List
Code Example
List<String> list =
map.values()
.stream()
.collect(Collectors.toList());
System.out.println(list);
Output:
[Ram, John, Sam]
Explanation
Create Employee class
Code Example
Employee class
class Employee {
int id;
String name;
double salary;
Employee(int id, String name, double salary) {
this.id = id;
this.name = name;
this.salary = salary;
}
public int getId() { return id; }
public String getName() { return name; }
public double getSalary() { return salary;
}}
cont..
Explanation
Create List
Code Example
List<Employee> list = Arrays.asList( new Employee(1, "Ram", 50000), new Employee(2, "John", 70000), new Employee(3, "Sam", 40000) );
Explanation
Employee with Filter
Code Example
Filter employee salary > 50000
list.stream()
.filter(emp -> emp.getSalary() > 50000)
.forEach(emp ->
System.out.println(emp.getName()));
Output:
John
Explanation
Convert List to Map
Code Example
Map<Integer, String> map =
list.stream()
.collect(Collectors.toMap(
Employee::getId,
Employee::getName
));
System.out.println(map);
Output:
{1=Ram, 2=John, 3=Sam}
Explanation
#white-Important Stream Methods:
Code Example
stream() create stream filter() filter data map() transform data collect() store result
Explanation
#white-Important Stream Methods:
Code Example
forEach() iterate sorted() sort count() count max() maximum min() minimum
Explanation
#white-Before Java 8: for(String name : list){ System.out.println(name); } #white-After Java 8: list.stream() .forEach(System.out::println);
Code Example
Explanation
Use Cases #white-Used in: •Employee filtering •Database data processing •Sorting data •Converting List to Map •Removing duplicates
Code Example
Explanation
#white-Stream is used to: •Process collections •Reduce code •Improve readability •Improve performance