Java 8 Optional Class
Java 8 introduced the Optional class in the java.util package to handle the problem of null values more gracefully. Instead of risking NullPointerException (NPE), Optional provides a container object that may or may not hold a non-null value.
Why Do We Need Optional
Traditionally, developers relied on null to represent the absence of a value, which often caused NullPointerException.
Example: Java program without the Optional Class
public class OptionalDemo {
public static void main(String[] args)
{
String[] words = new String[10];
String word = words[5].toLowerCase();
System.out.print(word);
}
}
Output:
Exception in thread "main" java.lang.NullPointerExceptionTo avoid abnormal termination, we use the Optional class. In the following example, we are using Optional. So, our program can execute without crashing.
Example: Program using Optional Class
import java.util.Optional;
// Driver Class
public class OptionalDemo {
// Main Method
public static void main(String[] args)
{
String[] words = new String[10];
Optional<String> checkNull = Optional.ofNullable(words[5]);
if (checkNull.isPresent()) {
String word = words[5].toLowerCase();
System.out.print(word);
}
else
System.out.println("word is null");
}
}
Output
word is null
Creating Optional Objects
- Optional.empty(): Returns an empty Optional.
- Optional.of(value): Returns an Optional containing the given non-null value.
- Optional.ofNullable(value): Returns an Optional describing the value if non-null, otherwise empty
Example 1: Using empty() and of()
import java.util.Optional;
class GFG {
public static void main(String[] args) {
String[] str = new String[5];
str[2] = "Geeks Classes are coming soon";
Optional<String> empty = Optional.empty();
System.out.println(empty);
Optional<String> value = Optional.of(str[2]);
System.out.println(value);
}
}
Output
Optional.empty Optional[Geeks Classes are coming soon]
Example 2: Using get(), hashCode() and isPresent()
import java.util.Optional;
class GFG {
public static void main(String[] args) {
String[] str = new String[5];
str[2] = "Geeks Classes are coming soon";
Optional<String> value = Optional.of(str[2]);
System.out.println(value.get());
System.out.println(value.hashCode());
System.out.println(value.isPresent());
}
}
Output
Geeks Classes are coming soon 1967487235 true
Common Methods in Optional
The Optional class offers methods such as isPresent() orElse() and ifPresent() to handle potentially null values more safely and functionally. The table below lists commonly used Optional methods and their descriptions.
Method | Description |
|---|---|
empty() | Returns an empty Optional instance |
of(T value) | Returns an Optional with the specified present non-null value. |
ofNullable(T value) | Returns an Optional describing the specified value if non-null, else empty |
equals(Object obj) | Checks if another object is "equal to" this Optional. |
filter(Predicate<? super T> predicate) | If a value is present and matches the predicate, returns an Optional with the value; else returns empty. |
flatMap(Function<? super T, Optional<U>> mapper) | If a value is present, applies a mapping function that returns an Optional; otherwise returns empty. |
get() | Returns the value if present, else throws NoSuchElementException. |
hashCode() | Returns the hash code of the value if present, otherwise returns 0. |
ifPresent(Consumer<? super T> consumer) | Returns true if a value is present, else false. |
map(Function<? super T, ? extends U> mapper) | If a value is present, applies the mapping function and returns an Optional describing the result (if non-null). |
orElse(T other) | Returns the value if present, otherwise returns the provided default value. |
orElseGet(Supplier<? extends T> other) | Returns the value if present, otherwise invokes the supplier and returns its result. |
orElseThrow(Supplier<? extends X> exceptionSupplier) | Returns the value if present, otherwise throws an exception provided by the supplier |
toString() | Returns a non-empty string representation of this Optional for debugging. |
