Function usage in java

Function interface is a functional interface used to represent a function that receives an input parameter and returns an output parameter. The specific usage is as follows: Create a Function instance: Use a lambda expression or method reference to create a Function. Call the apply method: Use the apply method to call Function, pass in input parameters and get the output result. The advantages of the Function interface include simplicity, reusability, composability, and parallelizability.

Function interface in Java

What is the Function interface?

Function interface is a functional interface used to represent a function that receives an input parameter and returns an output parameter.

Structure

@FunctionalInterface
public interface Function<T, R> {
    R apply(T t);
}

Usage

The usage of Function interface is very simple:

1. Create Function instance: Use lambda expression or method reference to create Function instance.
2. Call the apply method: Use the apply method to call Function, pass in the input parameters and get the output result.

Example

The following code creates a Function instance, converts the string to uppercase and returns:

Function<String, String> toUpperCase = s -> s.toUpperCase();
String result = toUpperCase.apply("hello"); // result 为 "HELLO"

Advantages

Using the Function interface has the following advantages:

• Conciseness: lambda expressions or method references provide a concise way to represent functions.
• Reusability: Function instances can be reused, thereby reducing duplicate code.
• Composability: Function can be combined together to form more complex functions.
• Parallelizability: Function interface can be used for parallel processing.

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