Stream API Tutorial

StreamApiTutorialApplication.java

package com.dailycodebuffer.streamapi;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

import java.util.*;
import java.util.stream.Collectors;
import java.util.stream.Stream;

@SpringBootApplication
public class StreamApiTutorialApplication {

    static List<Employee> employees = new ArrayList<>();
    static {
        employees.add(
                new Employee("Shabbir", "Dawoodi", 5000.0, List.of("Project 1","Project 2"))
        );

        employees.add(
                new Employee("Nikhil", "Gupta", 6000.0, List.of("Project 1","Project 3"))
        );

        employees.add(
                new Employee("Shivam", "Kumar", 5500.0, List.of("Project 3","Project 4"))
        );

    }

    public static void main(String[] args) {
        //SpringApplication.run(StreamApiTutorialApplication.class, args);

        //foreach
        employees.stream()
                .forEach(employee -> System.out.println(employee));


        //map
        //collect
        Set<Employee> increasedSal =
                employees.stream()
                .map(employee -> new Employee(
                        employee.getFirstName(),
                        employee.getLastName(),
                        employee.getSalary()  * 1.10,
                        employee.getProjects()
                ))
                .collect(Collectors.toSet());
        System.out.println(increasedSal);


        //filter
        //findFirst
        List<Employee> filterEmployee =
                employees
                .stream()
                .filter(employee -> employee.getSalary() > 5000.0)
                .map(employee -> new Employee(
                        employee.getFirstName(),
                        employee.getLastName(),
                        employee.getSalary()  * 1.10,
                        employee.getProjects()
                ))
                .collect(Collectors.toList());

        System.out.println(filterEmployee);


       Employee firstEmployee =
                employees
                        .stream()
                        .filter(employee -> employee.getSalary() > 7000.0)
                        .map(employee -> new Employee(
                                employee.getFirstName(),
                                employee.getLastName(),
                                employee.getSalary()  * 1.10,
                                employee.getProjects()
                        ))
                        .findFirst()
                        .orElse(null);
        System.out.println(firstEmployee);


        //flatMap
        String projects =
                employees
                .stream()
                .map(employee -> employee.getProjects())
                .flatMap(strings -> strings.stream())
                .collect(Collectors.joining(","));
        System.out.println(projects);

        //short Circuit operations
        List<Employee> shortCircuit =
                employees
                .stream()
                .skip(1)
                .limit(1)
                .collect(Collectors.toList());
        System.out.println(shortCircuit);


        //Finite Data
        Stream.generate(Math::random)
                .limit(5)
                .forEach(value -> System.out.println(value));

        //sorting
        List<Employee> sortedEmployees =
                employees
                .stream()
                .sorted((o1, o2) -> o1.getFirstName()
                        .compareToIgnoreCase(o2.getFirstName()))
                .collect(Collectors.toList());
        System.out.println(sortedEmployees);


        //min or max
        employees
                .stream()
                .max(Comparator.comparing(Employee::getSalary))
                .orElseThrow(NoSuchElementException::new);

        //reduce
        Double totalSal =
                employees
                .stream()
                .map(employee -> employee.getSalary())
                .reduce(0.0,Double::sum);
        System.out.println(totalSal);

    }

}


public class Employee {

    private String firstName;
    private String lastName;
    private Double salary;
    private List<String> projects;

    @Override
    public String toString() {
        return "Employee{" +
                "firstName='" + firstName + '\'' +
                ", lastName='" + lastName + '\'' +
                ", salary=" + salary +
                ", projects=" + projects +
                '}';
    }

    public Employee(String firstName, String lastName, Double salary, List<String> projects) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.salary = salary;
        this.projects = projects;
    }

    public Employee() {
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public Double getSalary() {
        return salary;
    }

    public void setSalary(Double salary) {
        this.salary = salary;
    }

    public List<String> getProjects() {
        return projects;
    }

    public void setProjects(List<String> projects) {
        this.projects = projects;
    }
}