Optional orElseThrow() method in Java with examples
Last Updated :
30 Jul, 2019
The orElseThrow() method of java.util.Optional class in Java is used to get the value of this Optional instance if present. If there is no value present in this Optional instance, then this method throws the exception generated from the specified supplier.
Syntax:
public <X> T
orElseThrow(Supplier<X> exceptionSupplier)
throws X extends Throwable
Parameters: This method accepts supplier as a parameter of type X to throws an exception if there is no value present in this Optional instance.
Return supplier: This method returns the value of this Optional instance, if present. If there is no value present in this Optional instance, then this method throws the exception generated from the specified supplier.
Exception: This method throws NullPointerException if there is no value present in this Optional instance.
Below programs illustrate orElseThrow() method:
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(
"Value by orElseThrow("
+ "ArithmeticException::new) method: "
+ op.orElseThrow(
ArithmeticException:: new ));
}
}
|
Output:
Optional: Optional[9455]
Value by orElseThrow(ArithmeticException::new) method: 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(
"Value by orElseThrow("
+ "ArithmeticException::new) method: "
+ op.orElseThrow(
ArithmeticException:: new ));
}
catch (Exception e) {
System.out.println(e);
}
}
}
|
Output:
Optional: Optional.empty
java.lang.ArithmeticException
Reference: https://docs.oracle.com/javase/9/docs/api/java/util/Optional.html#orElseThrow-java.util.function.Supplier-
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