Java or else throw

A container object which may or may not contain a non-null value. If a value is present, isPresent() will return true and get() will return the value. Additional methods that depend on the presence or absence of a contained value are provided, such as orElse() (return a default value if value not present) and ifPresent() (execute a block of code if the value is present). This is a value-based class; use of identity-sensitive operations (including reference equality ( == ), identity hash code, or synchronization) on instances of Optional may have unpredictable results and should be avoided.

Method Summary

If a value is present, and the value matches the given predicate, return an Optional describing the value, otherwise return an empty Optional .

If a value is present, apply the provided Optional -bearing mapping function to it, return that result, otherwise return an empty Optional .

If a value is present in this Optional , returns the value, otherwise throws NoSuchElementException .

If a value is present, apply the provided mapping function to it, and if the result is non-null, return an Optional describing the result.

Returns an Optional describing the specified value, if non-null, otherwise returns an empty Optional .

Return the contained value, if present, otherwise throw an exception to be created by the provided supplier.

Methods inherited from class java.lang.Object

Method Detail

empty

of

ofNullable

Returns an Optional describing the specified value, if non-null, otherwise returns an empty Optional .

get

If a value is present in this Optional , returns the value, otherwise throws NoSuchElementException .

isPresent

ifPresent

filter

public OptionalT> filter(PredicateT> predicate)

If a value is present, and the value matches the given predicate, return an Optional describing the value, otherwise return an empty Optional .

map

public Optional map(FunctionT,? extends U> mapper)

If a value is present, apply the provided mapping function to it, and if the result is non-null, return an Optional describing the result. Otherwise return an empty Optional .

API Note: This method supports post-processing on optional values, without the need to explicitly check for a return status. For example, the following code traverses a stream of file names, selects one that has not yet been processed, and then opens that file, returning an Optional :

 Optional fis = names.stream().filter(name -> !isProcessedYet(name)) .findFirst() .map(name -> new FileInputStream(name));

flatMap

public Optional flatMap(FunctionT,Optional> mapper)

If a value is present, apply the provided Optional -bearing mapping function to it, return that result, otherwise return an empty Optional . This method is similar to map(Function) , but the provided mapper is one whose result is already an Optional , and if invoked, flatMap does not wrap it with an additional Optional .

orElse

orElseGet

orElseThrow

public Throwable> T orElseThrow(Supplier exceptionSupplier) throws X extends Throwable

Return the contained value, if present, otherwise throw an exception to be created by the provided supplier.

equals

it is also an Optional and;
both instances have no value present or;
the present values are «equal to» each other via equals() .

hashCode

toString

Returns a non-empty string representation of this Optional suitable for debugging. The exact presentation format is unspecified and may vary between implementations and versions.

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For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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How to do Java Optional if present do something or else throw?

Solution 1: You could use the call to throw an exception if your filter finds anything: Solution 2: Since you only care if a match was found, not what was actually found, you can use for this, and you don’t need to use at all: Solution 3: Here middle bracket is compulsory, else it is showing compile time exception and exception class must extends runtime exception I could not return the value coming from save function because it is saying that it is void method and not expecting return value.

How to do Java Optional if present do something or else throw?

What I want to do is, updating a customer if it is present but if there is no customer then throw an exception. But I could not find the correct stream function to do that. How can I achieve this ?

public Customer update(Customer customer) throws Exception < OptionalcustomerToUpdate = customerRepository.findById(customer.getId()); customerToUpdate.ifPresentOrElse(value -> return customerRepository.save(customer), throw new Exception("customer not found")); >

I could not return the value coming from save function because it is saying that it is void method and not expecting return value.

As Guillaume F. already said in the comments, you could just use orElseThrow here:

Customer customer = customerRepository.findById(customer.getId()) .orElseThrow(() -> new Exception("customer not found")); return customerRepository.save(customer);

By the way, avoid throwing Exception , as that exception is too broad. Use a more specific type, like NotFoundException .

Java — How to execute logic on Optional if not present?, Rather use Java 9 or use if, else. vavr is not very nice – senseiwu. Dec 11, 2018 at 14:50. this is excessively complex just for a straight if then else! – JBarros35. this one will return Optional if present or Optional.empty() if not present. So now let’s get to the solution,

Optional ifPresentOrElse() method in Java with examples

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

public void ifPresentOrElse(Consumer 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.

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

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-

How to handle and log Optional or else throw custom, How to handle and log Optional or else throw custom exception in java? Ask Question Asked 1 year ago. also required which is not present in exception case. java exception logging optional. Share. Improve this question. Follow edited Aug 10, 2021 at 10:11. Java logging and throwing exception.

Optional orElseThrow() method in Java with examples

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.

public T orElseThrow(Supplier 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:

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What is the Optional.orElseThrow method in Java?

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In Java, the Optional object is a container object which may or may not contain a value. We can replace the multiple null check using the Optional object’s isPresent method.

The Optional class is present in the java.util package. Read more about the Optional class here.

The orElseThrow method will return the value present in the Optional object. If the value is not present, then the supplier function passed as an argument is executed and an exception created on the function is thrown.

public T orElseThrow(Supplier exceptionSupplier) throws X extends Throwable

Argument

The argument is the function to be executed if the Optional object is empty no value present in the Optional object . The supplier function should return the exception to be thrown.

Return value

If the Optional object contains a value, then the value is returned. Otherwise, the exception created by the supplier function is returned.

This method throws NullPointerException if no value is present and the supplier function is null .

Code

The below code denotes how to use the orElseThrow method.

import java.util.Optional;
 class OptionalOrElseThrowExample  public static void main(String[] args) throws Exception Optional optional1 = Optional.of(1);
 System.out.println("Optional1 : " + optional1);
 Integer val = optional1.orElseThrow(()->  return new Exception("no value present in Optional object");
 >);
 System.out.println("Value at Optional1 is : " + val);
 Optional optional2 = Optional.empty();
 System.out.println("\nOptional2 : " + optional2);
 val = optional2.orElseThrow(()->  return new Exception("no value present in Optional object");
 >);
 >
>

Explanation

In line number 1, we import the Optional class.
In line number 5, we create an Optional object of the Integer type with value 1 using of method.
In line number 7, we call the orElseThrow method on the optional1 object. For the orElseThrow method, a supplier function that returns an Exception object is passed as an argument. This method returns 1 because the optional1 object contains the value.
In line number 12, we use the empty method to get an empty Optional object of the Integer type. The returned object doesn’t have any value.
In line number 12, we call the orElseThrow method on the optional2 object. For the orElseThrow method, a supplier function that returns an Exception object is passed as an argument. This method throws the Exception returned by the supplier function because the optional2 object doesn’t have any value.

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