How to Use Method References with Parameters in Java Streams?

Question

How can I call a method with parameters using method references within Java Streams?

nodes.values().stream().forEach(node -> node.findChildren(name, result));

Answer

Using method references in Java Streams improves code readability. However, when your method requires parameters, the direct use of method references is not straightforward. Let's explore how to manage this using a practical example.

nodes.values().stream().forEach(node -> node.findChildren(name, result));

Causes

  • Method references cannot take parameters directly for additional arguments.
  • Java does not support partial application of functions directly in the context of method references.

Solutions

  • Use lambda expressions instead of method references where additional parameters are needed.
  • Utilize static utility methods that can wrap calls to existing methods with fixed parameters, using them in place of method references.

Common Mistakes

Mistake: Trying to use method references directly with parameters.

Solution: Use a lambda expression instead to explicitly pass the parameters.

Mistake: Not understanding that method references require matching parameter types.

Solution: Ensure method signatures match or use wrappers if necessary.

Helpers

  • Java Streams
  • method references
  • Java method references with parameters
  • lambda expressions Java
  • stream API Java

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