How to Use Optional class in Java

Optional is class java.util.Optional<T> introduce in java 1.8 version . Optional class is container class to represent the existence or absence of value .

These are some basic method of Optional class

  isPresent :- To check existence or absence of value in Optional class . 

  get :-   If object present in Optional class container then get method object from Optional class       container  otherwise throws a java.util.NoSuchElementException.

 orElse:-  If object present in Optional class container then get method object from Optional class container otherwise throws an Exception So to avoid this exception you can return another default object in case of exception.

  

Note :- Optional class also have primitive type representation of Optional class like

1.OptionalInt 

2.OptionalLong 

3. OptionalDouble

Optional Class Java Application 

OptionalApplication.java

package in.jk.java8.stream;

import java.util.List;

import java.util.Optional;

import java.util.OptionalDouble;

import java.util.OptionalInt;

import java.util.OptionalLong;

import in.jk.java8.Employee;

public class OptionalApplication {

public static void main(String[] args) {

System.out.println("Use Of Optional class Application .....\n");

Optional<Employee> employeeContainer = null;

List<Employee> employees = Employee.getEmployeeList();

employeeContainer = employees.stream()

                     .filter(employee -> employee.getSalary() > 2000)

                     .findFirst();

if (employeeContainer.isPresent()) {

Employee employee2 = employeeContainer.get();

System.out.println("Empoyee by Get :: " + employee2);

}

employeeContainer = employees.stream()

                      .filter(employee -> employee.getSalary() > 20000)

                      .findFirst();

try {

Employee employee = employeeContainer.get();

System.out.println("Employee by GET :: " + employee);

} catch (Exception e) {

System.out.println("\nIf Employee No Prsesent in Optional Class Container :: ");

System.out.println("Error :: " + e);

}

employeeContainer = employees.stream()

                                     .filter(employee -> employee.getSalary() > 2000)

                                     .findFirst();

                        Employee masterEmployee = new Employee();

masterEmployee.setEmpId(1);

masterEmployee.setName("John");

masterEmployee.setSalary(1);

masterEmployee.setCompany("Google");

employeeContainer.orElse(masterEmployee);

Employee employee = employeeContainer.orElse(masterEmployee);

System.out.println("\n Employee by orElse if Employee is present in Optinal :: " +                                  employee);

employeeContainer = employees.stream()

                                     .filter(emp -> emp.getSalary() > 20000)

                                     .findFirst();

Employee employee1 = employeeContainer.orElse(masterEmployee);

System.out.println("Employee by orElse if Employee is not present in Optinal :: " +                                 employee1);

System.out.println("\n----Use of primitive type representation of Optional---------\n");

OptionalInt optionalInt = employees.stream()

                           .filter(emp -> emp.getSalary() > 2000)

                           .mapToInt(Employee::getSalary)

                           .max();

System.out.println("Max Salary by OptionalInt :: "+optionalInt);

OptionalLong optionalLong = employees.stream()

                             .filter(emp -> emp.getSalary() > 2000)

                             .mapToLong(Employee::getSalary)

                             .max();

System.out.println("Max Salary by OptionalLong :: "+optionalLong);

OptionalDouble optionalDouble = employees.stream()

                                 .filter(emp -> emp.getSalary() > 2000)

                                 .mapToDouble(Employee::getSalary)

                                 .max();

System.out.println("Max Salary by OptionalDouble :: "+optionalDouble);

}

}

Employee.java

package in.jk.java8;

import java.util.ArrayList;

import java.util.List;

public class Employee {

private int empId;

private String name;

private String company;

private int salary;

//Getters and Setters

@Override

public String toString() {

return "Employee [empId=" + empId + ", name=" + name + ", company=" + company + ",                      salary=" + salary + "]";

}

public static  List<Employee>getEmployeeList() {

List<Employee> empList =new ArrayList<Employee>();

Employee  employee = new Employee();

        employee.setEmpId(1);

        employee.setName("J K");

        employee.setCompany("Google");

        employee.setSalary(1000);

        

        Employee  employee1 = new Employee();

        employee1.setEmpId(2);

        employee1.setName("J K");

        employee1.setCompany("Google");

        employee1.setSalary(2000);

        

        Employee  employee2 = new Employee();

        employee2.setEmpId(3);

        employee2.setName("J K");

        employee2.setCompany("Google");

        employee2.setSalary(3000);

        

        Employee  employee3 = new Employee();

        employee3.setEmpId(4);

        employee3.setName("SHA");

        employee3.setCompany("APAR");

        employee3.setSalary(4000);

        

        Employee  employee4 = new Employee();

        employee4.setEmpId(5);

        employee4.setName("HM");

        employee4.setCompany("PAYTM");

        employee4.setSalary(5000);

        

        Employee  employee5 = new Employee();

        employee5.setEmpId(5);

        employee5.setName("HM");

        employee5.setCompany("APAR");

        employee5.setSalary(6000);

        

        Employee  employee6 = new Employee();

        employee6.setEmpId(6);

        employee6.setName("JK");

        employee6.setCompany("APAR");

        employee6.setSalary(7000);

        

        Employee  employee7 = new Employee();

        employee7.setEmpId(7);

        employee7.setName("JK");

        employee7.setCompany("JET BRAINS");

        employee7.setSalary(8000);

        

        Employee  employee8 = new Employee();

        employee8.setEmpId(8);

        employee8.setName("AJ");

        employee8.setCompany("APAR");

        employee8.setSalary(9000);

        

        Employee  employee9 = new Employee();

        employee9.setEmpId(8);

        employee9.setName("AJ");

        employee9.setCompany("ADOBE");

        employee9.setSalary(10000);

        

        empList.add(employee);

        empList.add(employee1);

        empList.add(employee2);

        empList.add(employee3);

        empList.add(employee4);

        empList.add(employee5);

        empList.add(employee6);

        empList.add(employee7);

        empList.add(employee8);

        empList.add(employee9);

return empList;

}

}

Output in console ....

Use Of Optional class Application .....

Empoyee by Get :: Employee [empId=3, name=J K, company=Google, salary=3000]

 If Employee No Prsesent in Optional Class Container :: 

Error :: java.util.NoSuchElementException: No value present

 Employee by orElse if Employee is present in Optinal :: Employee [empId=3, name=J K, company=Google, salary=3000]

Employee by orElse if Employee is not present in Optinal :: Employee [empId=1, name=John, company=Google, salary=1]

----Use of primitive type representation of Optional---------

Max Salary by OptionalInt :: OptionalInt[10000]

Max Salary by OptionalLong :: OptionalLong[10000]

Max Salary by OptionalDouble :: OptionalDouble[10000.0]