Optional.require(String)?

[Sparky983]

Example usage:

/*
 * In reality this would be something where we don't 
 * know the value, but we are sure the optional has 
 * a value, rather than here where we know the value.
 */

class MyValueHolder {
  Optional<String> value = Optional.absent();
  void set(String s) { value = Optional.present(s); }
  Optional<String> get() { return value; }
}

MyValueHolder holder = ...;
holder.set("abc");
String s = holder.value().require("holder to have a value");

[Sparky983]

As mentioned in #39, here are some alternative names:

• Optional.orThrow(String)
• Optional.expect(String)

[Sparky983]

Will be introduced under the name expect as an experimental API.