Java8: Optional Class

Optional class is a Java8 introduction to ease null handling. This is a wrapper class that can be used with object(not with primitives).

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print(Optional.ofNullable(30));
print(Optional.ofNullable(null));

Let’s see how this method call will print the result.

private static void print(Optional<Integer> i) {
    i.ifPresent(System.out::println);}

This method will only print if the value is not null. so out put will be 30 only.

private static void print(Optional<Integer> i) {
    System.out.println(i.orElse(300));}

This method will print a default value of 300 if the given value is null, so output will be 30 and 300.

private static void print(Optional<Integer> i) {
    System.out.println( i.orElseGet(()-> 400));}

This method will call another method when the value is null. So out put will be 30 & 400.

private static void print(Optional<Integer> i) {
    if(i.isPresent()) // prints if not null
         System.out.println(i.get());
}

This method will print if the method is not null, so out put would be 30 only.

Java 9 Update

With Streams,

List<String> mylist=sourceList.stream()
        .flatMap(Optional::stream)
        .collect(Collectors.toList());

Let’s say you have a list with null values (sourceList). You can ignore null values like this

.flatMap(Optional::stream)

Out put of {q,f, ,r, ,w } will be {q,f,r,w} empty values are ignored from the stream.

Or Method

This method will give you a default value when the output is null.

Optional<String> op1=Optional.empty();
System.out.println(op1.get().toString());

Above code will give you a null value as we passing in a empty value. If we add below or method it will output a default value when the original value is null.

Optional<String> op1=Optional.empty();
op1=op1.or(() -> Optional.of("Not Present" ));
System.out.println(op1.get().toString());

ifPresentOrElse Method

This will allow you to pass two implementations based to handle null and non null values.

Optional<Integer> op=Optional.of(1);
op.ifPresentOrElse(integer -> System.out.println(integer), ()-> System.out.println("Not present"));

If you set op to a null value op=Optional.empty(); and test it again it will you will see the “Not present” is printed.

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