Java Stream Creation Code Example

This Java Program helps to create Stream from various collections like List, Set, Array, etc.

This Java Program helps to understand the way the Java Stream process can be processed. The developer can generate a Stream process from a Collection like List, Set, Map, Array List, and Array.

package com.kw.streamexample;

import java.util.Arrays;
import java.util.Collection;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.stream.Stream;

public class KWStreamCreationExample {

	public static void main(String[] args) {

		System.out.println("**** Stream Creation Program Example *****");

		Collection<String> collection = Arrays.asList("JAVA", "J2EE", "Spring", "Hibernate");
		Stream<String> stream = collection.stream();
		stream.forEach(System.out::println);

		System.out.println("****** List ******");

		List<String> list = Arrays.asList("JAVA", "J2EE", "Spring", "Hibernate", "Java Script");
		Stream<String> stream1 = list.stream();
		stream1.forEach(System.out::println);
		
		System.out.println("****** Set ******");

		Set<String> set = new HashSet<String>(list);
		Stream<String> stream2 = set.stream();
		stream2.forEach(System.out::println);

		System.out.println(Stream.empty().toString());
		
		System.out.println("****** Array ******");
		// Array can also be a source of a Stream
		Stream<String> streamArray1 = Stream.of("a", "b", "c");
		streamArray1.forEach(System.out::println);
		
		String[] stringArray = new String[] {"abc", "sdc", "wewe"};
		Stream<String> streamArray2 = Arrays.stream(stringArray);
		streamArray2.forEach(System.out::println);
		
		Stream<String> streamOfArrayPart = Arrays.stream(stringArray, 1, 3);
        streamOfArrayPart.forEach(System.out::println);
	}

}

Program Output:

**** Stream Creation Program Example *****
JAVA
J2EE
Spring
Hibernate
****** List ******
JAVA
J2EE
Spring
Hibernate
Java Script
****** Set ******
JAVA
Hibernate
Java Script
J2EE
Spring
java.util.stream.ReferencePipeline$Head@6ce253f1
****** Array ******
a
b
c
abc
sdc
wewe
sdc
wewe

package com.kw.streamexample;

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

public class KWStreamOfArrayExample {

	public static void main(String[] args) {
		System.out.println("Stream Creation From Array");

		System.out.println("************ 1 ***************");
		Stream<String> streamOfArray = Stream.of("A", "B", "c");
		streamOfArray.forEach(System.out::println);

		System.out.println("************ 2 ***************");
		String[] strArray = new String[] { "Ram", "Shyam", "Balram" };
		Stream<String> streamArray2 = Arrays.stream(strArray);
		streamArray2.forEach(System.out::println);

		System.out.println("************ 3 ***************");
		Stream<String> streamOfArrayPart = Arrays.stream(strArray, 1, 3);
		streamOfArrayPart.forEach(System.out::println);

	}

}

package com.kw.streamexample;

import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;

public class KWStreamListSorting {

	public static void main(String[] args) {

		List<String> fruits = new ArrayList<String>();
		fruits.add("Banana");
		fruits.add("Apple");
		fruits.add("Mango");
		fruits.add("Orange");

		List<String> sortedList = fruits.stream().sorted(Comparator.naturalOrder()).collect(Collectors.toList());
		System.out.println(sortedList);
		
		List<String> sortedList1 = fruits.stream().sorted((o1, o2) -> o1.compareTo(o2)).collect(Collectors.toList());
		System.out.println(sortedList1);
		
		List<String> sortedList2 = fruits.stream().sorted().collect(Collectors.toList());
		System.out.println(sortedList2);
		
		// Descending Order
		List<String> sortedList3 = fruits.stream().sorted(Comparator.reverseOrder()).collect(Collectors.toList());
		System.out.println(sortedList3);
		
		List<String> sortedList4 = fruits.stream().sorted((o1, o2) -> o2.compareTo(o1)).collect(Collectors.toList());
		System.out.println(sortedList4);	
		
	}

}

package com.kw.streamexample;

import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;

public class KWStreamListOfEmployeeSorting {

	public static void main(String[] args) {

		List<Employee> employees = new ArrayList<Employee>();
		employees.add(new Employee(10, "Ramesh", 30, 400000));
		employees.add(new Employee(20, "John", 29, 350000));
		employees.add(new Employee(30, "Tom", 30, 450000));
		employees.add(new Employee(40, "Pramod", 29, 500000));
		
		List <Employee> employeesSortedList1 = employees.stream().sorted((o1, o2) -> (int)(o1.getSalary() - o2.getSalary())).collect(Collectors.toList());
		System.out.println(employeesSortedList1);
		
		List <Employee> employeesSortedList2 = employees.stream().sorted(Comparator.comparingLong(Employee::getSalary)).collect(Collectors.toList());
		System.out.println(employeesSortedList2);
		
		// Descending order
		List <Employee> employeesSortedList3 = employees.stream().sorted((o1, o2) -> (int)(o2.getSalary() - o1.getSalary())).collect(Collectors.toList());
		System.out.println(employeesSortedList3);
		
		List <Employee> employeesSortedList4 = employees.stream().sorted(Comparator.comparingLong(Employee::getSalary).reversed()).collect(Collectors.toList());
		System.out.println(employeesSortedList4);
		

	}

}