Optional class -jdk 8 concept

package java8;

public class OptionalClassDemo {

            public static void main(String[] args) {

                        String []s1=new String[5];

                        String s2=s1[3].toLowerCase();

                        System.out.println(s2);

                       

            }

}

o/p:----------

Exception in thread "main" java.lang.NullPointerException

       at java8.OptionalClassDemo.main(OptionalClassDemo.java:6)

package java8;

import java.util.Optional;

public class OptionalClassDemo1 {

            public static void main(String[] args) {

                        String []s1=new String[5];

                        Optional<String> kk = Optional.ofNullable(s1[3]);

                        if(kk.isPresent())

                        {

                                    String s2 = s1[3].toLowerCase();

                                    System.out.println(s2);

                        }

                       

                        else

                        {

                                    System.out.println("String value is not present");

                        }

                                               

            }

}

o/p:---------------

String value is not present

========================================================================================

package java8;

import java.util.Optional;

public class OptionalClassDemo3 {

            public static void main(String[] args) {

                        String s1[]=new String[5];

                        s1[3]="govind ballabh khan";

                        Optional<String> kk = Optional.ofNullable(s1[3]);

                        if(kk.isPresent())

                        {

                        String s2 = s1[3].toLowerCase();

                        System.out.println(s2);

                        }

                        else

                        {

                                    System.out.println("String value is not possible");

                        }

                       

            }

}

o/p:-------------------

govind ballabh khan

package java8;

import java.util.Optional;

public class OptionalClassDemo4 {

            public static void main(String[] args) {

                        String [] s1=new String[5];

                        s1[3]="Govind Ballabh Khan";

                        Optional<String> kk = Optional.ofNullable(s1[3]);

                        kk.ifPresent(System.out::println);// printing value by using method reference

                        System.out.println(kk.get());// printing value by using get method

                        System.out.println(s1[3].toLowerCase());

            }}

o/p:-----------------

Govind Ballabh Khan

Govind Ballabh Khan

govind ballabh khan

==========================================================================================

package java8;

import java.util.Optional;

public class OptionClassDemo5 {

            public static void main(String[] args) {

                        String s1[]=new String[5];

                        s1[3]="Govind Ballabh Khan";

                        Optional<Object> empty = Optional.empty();

                        System.out.println(empty);

                        Optional<String> op = Optional.of(s1[3]);

                        System.out.println(op);

                        System.out.println("Filtered Value="+op.filter((p)->p.equals("Mnc")));

                        System.out.println("Filtered Value="+op.filter((p)->p.equals("Govind Ballabh Khan")));

                        System.out.println("Getting values:"+op.get());

                        System.out.println("Getting HashCode:"+op.hashCode());

                        System.out.println("Is Value Present:"+op.isPresent());

                        System.out.println("Nullable Optional:"+op.ofNullable(s1[3]));

                        System.out.println("orElse:"+op.orElse("value is not present"));

                        System.out.println("orElse:"+empty.orElse("Value is not present"));

                        op.ifPresent((System.out::println));

                       

                       

                       

                       

                       

            }

}

o/p:------------------------

Optional.empty

Optional[Govind Ballabh Khan]

Filtered Value=Optional.empty

Filtered Value=Optional[Govind Ballabh Khan]

Getting values:Govind Ballabh Khan

Getting HashCode:-233837391

Is Value Present:true

Nullable Optional:Optional[Govind Ballabh Khan]

orElse:Govind Ballabh Khan

orElse:Value is not present

Govind Ballabh Khan

=======================================================================================