How to use Optional Class in Java8
Posted By : Dinesh Kumar | 27-Jul-2018
Java introduced another class Optional in jdk8. It is a public last class and used to manage NullPointerException in Java application. You must import java.util bundle to utilize this class. It gives methods which are utilized to check the nearness of significant worth for particular variable.
1. Case: Java Program without utilizing Optional
In the accompanying case, we are not utilizing Optional class. This program terminates strangely and throws a nullPointerException.
<html>
public class OptionalExample {
public static void main(String[] args) {
String[] str = new String[10];
String lowercaseString = str[5].toLowerCase();
System.out.print(lowercaseString);
}
}
</html>
Output:
Exception in thread "main" java.lang.NullPointerException
at lambdaExample.OptionalExample.main(OptionalExample.java:6)
2. Case: Java Program with utilizing Optional : To avoid the strange termination, we utilize Optional class. In the accompanying illustration, we are utilizing Optional. In this way, our program can execute without slamming.
Java Optional Example: If Value isn't Present
<html>
import java.util.Optional;
public class OptionalExample {
public static void main(String[] args) {
String[] str = new String[10];
Optional<String> checkNull = Optional.ofNullable(str[5]);
if(checkNull.isPresent()){/check for esteem is present or not
String lowercaseString = str[5].toLowerCase();
System.out.print(lowercaseString);
}else
System.out.println("string esteem isn't present");
}
}
</html>
Output:
string esteem isn't present
Java Optional Example: If Value is Present
<html>
import java.util.Optional;
public class OptionalExample {
public static void main(String[] args) {
String[] str = new String[10];
str[5] = "JAVA OPTIONAL CLASS EXAMPLE";//Setting an incentive for 5th file
Optional<String> checkNull = Optional.ofNullable(str[5]);
if(checkNull.isPresent()){/It Checks, esteem is present or not
String lowercaseString = str[5].toLowerCase();
System.out.print(lowercaseString);
}else
System.out.println("String esteem isn't present");
}
}
</html>
Output:
java optional class illustration
Another Java Optional Example
<html>
import java.util.Optional;
public class OptionalExample {
public static void main(String[] args) {
String[] str = new String[10];
str[5] = "JAVA OPTIONAL CLASS EXAMPLE";/Setting an incentive for 5th file
Optional<String> checkNull = Optional.ofNullable(str[5]);
checkNull.ifPresent(System.out::println);/printing an incentive by utilizing method reference
System.out.println(checkNull.get());/printing an incentive by utilizing get method
System.out.println(str[5].toLowerCase());
}
}
</html>
Output:
JAVA OPTIONAL CLASS EXAMPLE
JAVA OPTIONAL CLASS EXAMPLE
java optional class case
Java Optional Methods Example
<html>
import java.util.Optional;
public class OptionalExample {
public static void main(String[] args) {
String[] str = new String[10];
str[5] = "JAVA OPTIONAL CLASS EXAMPLE";/Setting an incentive for 5th record
//It returns an empty instance of Optional class
Optional<String> empty = Optional.empty();
System.out.println(empty);
//It returns a non-empty Optional
Optional<String> esteem = Optional.of(str[5]);
System.out.println("esteem: "+value.filter((s)- >s.equals("Abc")));
System.out.println("Filtered esteem: "+value.filter((s)- >s.equals("JAVA OPTIONAL CLASS EXAMPLE")));
//It returns estimation of an Optional. on the off chance that esteem isn't present, it throws a NoSuchElementException
System.out.println("Getting esteem: "+value.get());
//It returns hashCode of the esteem
System.out.println("Getting hashCode: "+value.hashCode());
//It returns true if esteem is present, otherwise false
System.out.println("Is esteem present: "+value.isPresent());
//It returns non-empty Optional if esteem is present, otherwise returns an empty Optional
System.out.println("Nullable Optional: "+Optional.ofNullable(str[5]));
//It returns esteem if accessible, otherwise returns determined esteem,
System.out.println("orElse: "+value.orElse("Value isn't present"));
System.out.println("orElse: "+empty.orElse("Value isn't present"));
value.ifPresent(System.out::println);/printing an incentive by utilizing method reference
}
}
</html>
Output:
Optional.empty
Filtered esteem: Optional.empty
Filtered esteem: Optional[JAVA OPTIONAL CLASS EXAMPLE]
Getting esteem: JAVA OPTIONAL CLASS EXAMPLE
Getting hashCode: - 619947648
Is esteem present: true
Nullable Optional: Optional[JAVA OPTIONAL CLASS EXAMPLE]
orElse: JAVA OPTIONAL CLASS EXAMPLE
orElse: Value isn't present
JAVA OPTIONAL CLASS EXAMPLE
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About Author
Dinesh Kumar
Dinesh Kumar is an experienced with knowledge of Spring Framework, Spring Boot, Java, Javascript, JQuery, AngularJs, and SQL.