Optional or() method in Java with examples
Last Updated :
30 Jul, 2019
The or() method of java.util.Optional class in Java is used to get this Optional instance if any value is present. If there is no value present in this Optional instance, then this method returns an Optional instance with the value generated from the specified supplier.
Syntax:
public Optional<T> or(Supplier<T> supplier)
Parameters: This method accepts supplier as a parameter of type T to generate an Optional instance with the value generated from the specified supplier.
Return supplier: This method returns this Optional instance, if any value is present. If there is no value present in this Optional instance, then this method returns an Optional instance with the value generated from the specified supplier.
Exception: This method throws NullPointerException if the supplying function is null or produces a null result.
Below programs illustrate or() method:
Note: As this method was added in Java 9, the programs need JDK 9 to execute.
Program 1:
import java.util.*;
import java.util.function.*;
public class GFG {
public static void main(String[] args)
{
Optional<Integer> op
= Optional.of( 9455 );
System.out.println( "Optional: "
+ op);
System.out.println( "Optional by or(() ->"
+ " Optional.of(100)) method: "
+ op.or(() -> Optional.of( 100 )));
}
}
|
Output:
Optional: Optional[9455]
Optional by or(() -> Optional.of(100)) method: Optional[9455]
Program 2:
import java.util.*;
import java.util.function.*;
public class GFG {
public static void main(String[] args)
{
Optional<Integer> op
= Optional.empty();
System.out.println( "Optional: "
+ op);
try {
System.out.println( "Optional by or(() ->"
+ " Optional.of(100)) method: "
+ op.or(() -> Optional.of( 100 )));
}
catch (Exception e) {
System.out.println(e);
}
}
}
|
Output:
Optional: Optional.empty
Optional by or(() -> Optional.of(100)) method: Optional[100]
Reference: https://docs.oracle.com/javase/9/docs/api/java/util/Optional.html#or-java.util.function.Supplier-
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