Java8 lambda-functioanl Interface-function interface

The concept of functional interface is added to Java 8. And added a new annotation @FunctionalInterfaceI

1 What is the functional interface function interface?

Functional Interface:functional interface only has 1 abstract method. This is the definition of the function interface. Simply understood, the function interface is actually an interface of an abstract method (interface).

2 Types of functional interfaces

Here I only introduce a few types of basic predicate<t>,consumer<t>,function<t, r>,supplier<t>

These functions are declared in the Java.util.function package, you can see the code on their own.

1 predicate<t>--receives the T (generics) Generic object and returns a Boolean

Boolean Test (T T);

Often used for judgment, e.g. Stream.filter (predicate<t>)

2 consumer<t>--receive Tgenerics) generic object, no return value

void Accept (T t)

Used as Consumer such as foreach (consumer<t>)

3 Function<t, r>--receive tgenerics) generic object, return R (generics) Generic Object

T-R

R apply (T t)

Example Stream.map (function<t, r>)

4 supplier<t>--provides tgenerics) generic objects (such as factories) that do not receive values

() T

3. Attention to Detail

The function interface does not allow only one method, because Java 8 adds a new default method. Therefore, a functional interface can also have multiple default methods. However, a functional interface can have only one abstract method.

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Java8 lambda-functioanl Interface-function interface