orElseorElseGetorElseThrow

orElseorElseGetorElseThrow is a shorthand reference to the trio of methods in Java's Optional type that handle empty values: orElse, orElseGet, and orElseThrow. They provide different strategies for obtaining a value when the Optional is empty and are commonly used to express fallback behavior in a fluent style.

orElse(T other) returns the contained value if present; otherwise it returns the provided other value. The other is evaluated eagerly at the time of the call, so any computation used to create other will occur regardless of whether a value exists.

orElseGet(Supplier<? extends T> supplier) returns the contained value if present; otherwise it calls supplier.get() to obtain a fallback value. The supplier is evaluated lazily, meaning it runs only when the Optional is empty, which can save work for expensive computations.

orElseThrow() returns the contained value if present; otherwise it throws NoSuchElementException. There is also orElseThrow(Supplier<? extends X> exceptionSupplier) to throw a custom exception supplied by the caller.

Usage considerations include choosing between eager and lazy fallbacks (orElse vs orElseGet) and deciding whether a missing value should be treated as an error (orElseThrow) or as a normal default. These methods help avoid null checks by providing explicit handling paths for present and absent values.

Examples:

Optional<String> opt = Optional.ofNullable(getName());

String a = opt.orElse("default");

String b = opt.orElseGet(() -> computeDefaultName());

String c = opt.orElseThrow(() -> new IllegalStateException("Name missing"));