Java中option&optional

How to process nullable value in elegant way

optional in java

• create optional
  • of, set a null will throw nullPointerException
  • ofNullable, set a null will throw no suchElementException
• orElse will create a default value whatever this.isPresent is true or not
• getOrElse the opposite of “orElse” operation
• handle exception
  • orElseThrow works for optional.ofNullable
• filter
  • This is used to check logic with different judge condition. incompatible for list operation
  • If list, we can use stream filter directly
• transforming
  • map
    • convert a optional value to other value
    • also can filter a new list from original list with java stream operation
  • flatMap
    • for nested optional object, no need to unwrap, which can get it directly.
• serialize
  • with Jackson to treat an empty Optional as null, and to treat a present Optional as a field representing its value.

option in vavr

• option is used to eliminate nullable check, which can make our code more safe
• you can add the following dependency for using option vavr

  <dependency>
      <groupId>io.vavr</groupId>
      <artifactId>vavr</artifactId>
      <version>0.9.0</version>
  </dependency>

• create option
  • Option.of, then we can use getOrElse to get actual value or set a default value for returning
• Tuple
• Try
  • replace try-catch block
  • if it is failure, can use getOrElse
  • if dev wants to throw exception, can use getOrElseThrow
• function Interface
  • Function
  • BiFunction
  • Function[num]
• collections
  • include list, array, set, map, etc.
• validation
  • combine
  • valid
  • invalid
  • ap
• Match Pattern

  Match(input).of(
  Case(...
  ))

source code