What is the Key Difference Between `map()` and `flatMap()` in Java 8 Streams?

Comparing map() and flatMap() Methods in Java 8 Streams

Streams in Java 8 offer a powerful set of operations for working with collections of data, including map() and flatMap(). Both these methods take a Stream as input and return a new Stream, but they differ in their behavior based on the number of output values produced for each input value.

map()

• Accepts a Function that converts each input value to a single output value.
• The output Stream contains the same number of elements as the input Stream.

flatMap()

• Accepts a Function that conceptually converts each input value to a Stream of zero or more output values.
• The output Stream is "flattened" by collecting all the output values from the mapped Streams into a single Stream.

Key Differences

• Output Size: map() produces one output value for each input value, while flatMap() produces an arbitrary number of output values for each input value.
• Mapper Function: map() requires a Function that maps an input value to an output value, while flatMap() requires a Function that maps an input value to a Stream.

Use Cases

• map(): Converts each element in a Stream using a single function. For example, converting a stream of strings to uppercase.
• flatMap(): Used when you need to extract multiple values from each element in a Stream and then flatten the results into a single Stream. For example, flattening a Stream of lists into a Stream of individual elements.

The above is the detailed content of What is the Key Difference Between `map()` and `flatMap()` in Java 8 Streams?. For more information, please follow other related articles on the PHP Chinese website!