Optional

PROBLEM

public Foo doSomething() {
    return null; 
}


Foo foo = doSomething();
if (foo == null) {
    // handle null case...
}
else {
    // do something with the foo object...
}

SOLUTION

public Optional<Foo> doSomething() {

	Optional<Foo> foo = Optional.of(new Foo());  // populated Optional
	Optional<Foo> foo = Optional.of(null);      // throws NullPointerException
	
	// Right way
	Optional<Foo> foo1 = Optional.ofNullable(new Foo());  // populated Optional
	Optional<Foo> foo2 = Optional.ofNullable(null);       // empty Optional
	
	Optional<Foo> populated = // ...populated Optional...
	populated.isPresent();    // true
	populated.isEmpty();      // false	
	

}

Foo foo = doSomething()
		.orElse(new Foo());
		
Foo foo = doSomething()
		.orElseThrow(SomeException::new);		
		
// we must use additional methods
Foo foo = doSomething();  // - will not compile

Optional<Foo> possibleFoo = doSomething();

Foo foo = possibleFoo
		.orElseGet(() -> { /* ...lazily create a Foo object... */ });
		
possibleFoo.ifPresent(foo -> { /* ...do something with foo... */ });		

possibleFoo.ifPresentOrElse(
    foo -> { /* ...do something with foo... */ },
    () -> { /* ...do something when no foo found... */ }
);

// for Example

public Optional<Bar> findBar() {
    // ...return a populated Bar if it could be found...
}

findBar().ifPresent(bar -> bar.update());