Java : OptionalLong with Examples

public class LongSample {

    private final long value;

    public LongSample() {
        this.value = -1;
    }

    public LongSample(long value) {
        if (value < 0) {
            throw new IllegalArgumentException();
        }

        this.value = value;
    }

    public OptionalLong getValue() {
        if (value == -1) {
            return OptionalLong.empty();
        } else {
            return OptionalLong.of(value);
        }
    }
}

final var sample = new LongSample(123);

sample.getValue().ifPresent(value -> {
    System.out.println("value : " + value);
});

// Result
// ↓
//value : 123

final var sample = new LongSample();

sample.getValue().ifPresentOrElse(value -> {
    System.out.println("value : " + value);
}, () -> {
    System.out.println("value : empty!");
});

// Result
// ↓
//value : empty!

static OptionalLong empty ()

Returns an empty OptionalLong instance.

final var opt = OptionalLong.empty();
System.out.println(opt); // OptionalLong.empty
System.out.println(opt.isEmpty()); // true

final var opt = OptionalLong.empty();

try {
    final var value = opt.orElseThrow();
} catch (NoSuchElementException e) {
    System.out.println(e);
}

// Result
// ↓
//java.util.NoSuchElementException: No value present

boolean equals (Object obj)

Indicates whether some other object is "equal to" this OptionalLong.

final var opt1 = OptionalLong.of(100);
final var opt2 = OptionalLong.of(100);
final var opt3 = OptionalLong.of(999);

System.out.println(opt1.equals(opt2)); // true
System.out.println(opt1.equals(opt3)); // false

final var opt1 = OptionalLong.of(123);
final var opt2 = OptionalLong.empty();

System.out.println(opt1.equals(opt2)); // false

final var opt1 = OptionalLong.empty();
final var opt2 = OptionalLong.empty();

System.out.println(opt1.equals(opt2)); // true

long getAsLong ()

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

final var sample = new LongSample(123);

final var opt = sample.getValue();
if (opt.isPresent()) {
    System.out.println(opt.getAsLong()); // 123
}

final var sample = new LongSample();
final var opt = sample.getValue();

try {
    final var value = opt.getAsLong();
} catch (NoSuchElementException e) {
    System.out.println(e);
}

// Result
// ↓
//java.util.NoSuchElementException: No value present

int hashCode ()

Returns the hash code of the value, if present, otherwise 0 (zero) if no value is present.

final var ret1 = OptionalLong.empty().hashCode();
System.out.println(ret1); // 0

final var ret2 = OptionalLong.of(123).hashCode();
System.out.println(ret2); // 123

final var ret3 = OptionalLong.of(-789).hashCode();
System.out.println(ret3); // 788

void ifPresent (LongConsumer action)

If a value is present, performs the given action with the value, otherwise does nothing.

final var sample = new LongSample(123);

System.out.println("-- ifPresent --");
sample.getValue().ifPresent(value -> {
    System.out.println("  action : " + value);
});

System.out.println("-- end --");

// Result
// ↓
//-- ifPresent --
//  action : 123
//-- end --

final var sample = new LongSample();

System.out.println("-- ifPresent --");
sample.getValue().ifPresent(value -> {
    System.out.println("  action : " + value);
});

System.out.println("-- end --");

// Result
// ↓
//-- ifPresent --
//-- end --

void ifPresentOrElse (LongConsumer action, Runnable emptyAction)

If a value is present, performs the given action with the value, otherwise performs the given empty-based action.

final var sample = new LongSample(123);

System.out.println("-- ifPresentOrElse --");
sample.getValue().ifPresentOrElse(value -> {
    System.out.println("  action : " + value);
}, () -> {
    System.out.println("  emptyAction!");
});

System.out.println("-- end --");

// Result
// ↓
//-- ifPresentOrElse --
//  action : 123
//-- end --

final var sample = new LongSample();

System.out.println("-- ifPresentOrElse --");
sample.getValue().ifPresentOrElse(value -> {
    System.out.println("  action : " + value);
}, () -> {
    System.out.println("  emptyAction!");
});

System.out.println("-- end --");

// Result
// ↓
//-- ifPresentOrElse --
//  emptyAction!
//-- end --

boolean isEmpty ()

If a value is not present, returns true, otherwise false.

final var sample = new LongSample(123);

if (sample.getValue().isEmpty()) {
    System.out.println("empty!");
} else {
    System.out.println("present!");
}

// Result
// ↓
//present!

final var sample = new LongSample();

if (sample.getValue().isEmpty()) {
    System.out.println("empty!");
} else {
    System.out.println("present!");
}

// Result
// ↓
//empty!

boolean isPresent ()

If a value is present, returns true, otherwise false.

final var sample = new LongSample(123);

if (sample.getValue().isPresent()) {
    System.out.println("present!");
} else {
    System.out.println("empty!");
}

// Result
// ↓
//present!

final var sample = new LongSample();

if (sample.getValue().isPresent()) {
    System.out.println("present!");
} else {
    System.out.println("empty!");
}

// Result
// ↓
//empty!

static OptionalLong of (long value)

Returns an OptionalLong describing the given value.

final var opt1 = OptionalLong.of(123);
System.out.println(opt1); // OptionalLong[123]

final var opt2 = OptionalLong.of(-789);
System.out.println(opt2); // OptionalLong[-789]

long orElse (long other)

If a value is present, returns the value, otherwise returns other.

final var sample = new LongSample(100);

final var ret = sample.getValue().orElse(9999);
System.out.println(ret); // 100

final var sample = new LongSample();

final var ret = sample.getValue().orElse(9999);
System.out.println(ret); // 9999

long orElseGet (LongSupplier supplier)

If a value is present, returns the value, otherwise returns the result produced by the supplying function.

final var sample = new LongSample(100);

final var ret = sample.getValue().orElseGet(() -> {
    System.out.println("action!");
    return 9999;
});

System.out.println("ret = " + ret);

// Result
// ↓
//ret = 100

final var sample = new LongSample();

final var ret = sample.getValue().orElseGet(() -> {
    System.out.println("action!");
    return 9999;
});

System.out.println("ret = " + ret);

// Result
// ↓
//action!
//ret = 9999

long orElseThrow ()

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

final var sample = new LongSample(123);

final var opt = sample.getValue();
if (opt.isPresent()) {
    System.out.println(opt.orElseThrow()); // 123
}

final var sample = new LongSample();
final var opt = sample.getValue();

try {
    final var value = opt.orElseThrow();
} catch (NoSuchElementException e) {
    System.out.println(e);
}

// Result
// ↓
//java.util.NoSuchElementException: No value present

<X extends Throwable> long orElseThrow (Supplier<? extends X> exceptionSupplier)

If a value is present, returns the value, otherwise throws an exception produced by the exception supplying function.

final var sample = new LongSample(123);

final var opt = sample.getValue();
if (opt.isPresent()) {
    final var value = opt.orElseThrow(IllegalStateException::new);
    System.out.println(value); // 123
}

final var sample = new LongSample();

try {
    final var value = sample.getValue().orElseThrow(() -> {
        throw new IllegalStateException("empty!");
    });
} catch (IllegalStateException e) {
    System.out.println(e);
}

// Result
// ↓
//java.lang.IllegalStateException: empty!

LongStream stream ()

If a value is present, returns a sequential LongStream containing only that value, otherwise returns an empty LongStream.

final var sample = new LongSample(123);

final var array = sample.getValue().stream().toArray();
System.out.println(Arrays.toString(array)); // [123]

final var count = sample.getValue().stream().count();
System.out.println(count); // 1

final var sample = new LongSample();

final var array = sample.getValue().stream().toArray();
System.out.println(Arrays.toString(array)); // []

final var count = sample.getValue().stream().count();
System.out.println(count); // 0

String toString ()

Returns a non-empty string representation of this OptionalLong suitable for debugging.

final var ret1 = OptionalLong.empty().toString();
System.out.println(ret1); // OptionalLong.empty

final var ret2 = OptionalLong.of(123).toString();
System.out.println(ret2); // OptionalLong[123]

final var ret3 = OptionalLong.of(-789).toString();
System.out.println(ret3); // OptionalLong[-789]