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:

// Java program to demonstrate 
// Optional.orElseThrow() method 
  
importjava.util.*; 
importjava.util.function.*; 
  
publicclassGFG { 
  
    publicstaticvoidmain(String[] args) 
    { 
  
        // create a Optional 
        Optional<Integer> op 
            = Optional.of(9455); 
  
        // print supplier 
        System.out.println("Optional: "
                           + op); 
  
        // orElseThrow supplier 
        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:

// Java program to demonstrate 
// Optional.orElseThrow() method 
  
importjava.util.*; 
importjava.util.function.*; 
  
publicclassGFG { 
  
    publicstaticvoidmain(String[] args) 
    { 
  
        // create a Optional 
        Optional<Integer> op 
            = Optional.empty(); 
  
        // print supplier 
        System.out.println("Optional: "
                           + op); 
  
        try{ 
  
            // orElseThrow supplier 
            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-

Optional isPresent() Method in Java

ShubhamMaurya3

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Optional orElseThrow() method in Java with examples

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