ifPresent and isPresent

Learn checks with ifPresent and isPresent.

Conditional action: ifPresent

ifPresent(Consumer) runs the given Consumer when the value is present; it does nothing otherwise. This is the cleanest way to use the value without an explicit isPresent check.

Example: opt.ifPresent(value -> System.out.println(value)). If opt is present the value is printed; if empty, nothing happens. ifPresent fits side-effecting operations; it is not for cases that expect a return value. When you also want an action for the absent case, use ifPresentOrElse.

Avoiding get

Optional.get() returns the value directly; but it throws NoSuchElementException when the value is absent. Calling get without a check is therefore risky.

Prefer ifPresent, orElse or orElseThrow instead. Example: opt.ifPresent(v -> use(v)). The empty case is handled explicitly; no unexpected error. If you are certain a value exists, get still works; in that case a comment explaining why is good practice.

Exercise Print a value with ifPresent

Create an Optional<String> with Optional.of("Mia"). Use ifPresent with a lambda to print the value prefixed by "Hello " via System.out.println.

Show example solution

import java.util.Optional;

public class IfPresentExample {
    public static void main(String[] args) {
        Optional<String> name = Optional.of("Mia");
        name.ifPresent(n -> System.out.println("Hello " + n));
    }
}

Test yourself

Match the Optional inspection methods

ifPresent

Takes a Consumer
isPresent

Returns boolean
isEmpty

Is it empty
ifPresentOrElse

Takes two Consumers
Which method returns a boolean?
- ifPresent
- get
- isPresent
- map
Show answer

isPresent — isPresent returns the value's presence as a boolean.

Complete the isPresent check

boolean present = opt.____();

Show answer

boolean present = opt.isPresent();

Next lesson: Summary - Optional

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