Optional ifPresentOrElse() method in Java with examples

Optional orElse() method in Java with examples

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The ifPresentOrElse(Consumer, Runnable) method of java.util.Optional class helps us to perform the specified Consumer action the value of this Optional object. If a value is not present in this Optional, then this method performs the given empty-based Runnable emptyAction, passed as the second parameter

Syntax:

public void ifPresentOrElse(Consumer<T> action,
                            Runnable emptyAction)

Parameters: This method accepts two parameters:

action: which is the action to be performed on this Optional, if a value is present.
emptyAction: which is the empty-based action to be performed, if no value is present.

Return value: This method returns nothing.

Exception: This method throw NullPointerException if a value is present and the given action is null, or no value is present and the given empty-based action is null.

Below programs illustrate ifPresentOrElse() method:

Note: As this method was added in Java 9, the programs need JDK 9 to execute.

Program 1:

// Java program to demonstrate 
// Optional.ifPresentOrElse() method 
  
import java.util.*; 
  
public class GFG { 
  
    public static void main(String[] args) 
    { 
  
        // create a Optional 
        Optional<Integer> op 
            = Optional.of(9455); 
  
        // print value 
        System.out.println("Optional: "
                           + op); 
  
        // apply ifPresentOrElse 
        op.ifPresentOrElse( 
            (value) 
                -> { System.out.println( 
                         "Value is present, its: "
                         + value); }, 
            () 
                -> { System.out.println( 
                         "Value is empty"); }); 
    } 
} 

Output:

Optional: Optional[9455]
Value is present, its: 9455

Program 2:

// Java program to demonstrate 
// Optional.ifPresentOrElse method 
  
import java.util.*; 
  
public class GFG { 
  
    public static void main(String[] args) 
    { 
  
        // create a Optional 
        Optional<Integer> op 
            = Optional.empty(); 
  
        // print value 
        System.out.println("Optional: "
                           + op); 
  
        try { 
  
            // apply ifPresentOrElse 
            op.ifPresentOrElse( 
                (value) 
                    -> { System.out.println( 
                             "Value is present, its: "
                             + value); }, 
                () 
                    -> { System.out.println( 
                             "Value is empty"); }); 
        } 
        catch (Exception e) { 
            System.out.println(e); 
        } 
    } 
} 

Output:

Optional: Optional.empty
Value is empty

Reference: https://docs.oracle.com/javase/9/docs/api/java/util/Optional.html#ifPresentOrElse-java.util.function.Consumer-java.lang.Runnable-

Tags:

#Java - util package #Java-Functions #Java-Optional #Java #Java

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