Java 8 new Features 1-function interface

Java 8 new features 1-function interface Original

LAMBDA Expression Basic structure:

(PARAM1,PARAM2,PARAM3), { code block }

Example 1:

Package Com.demo.jdk8;import Java.util.arrays;import Java.util.list;import Java.util.function.consumer;public class Test2 {public static void main (string[] args) {for_test (); For_newmethod (); For_lambda ();} public static void For_test () {list<integer> List = Arrays.aslist (1,2,3,4,5,6), for (Integer i:list) { System.out.println (i);}} public static void For_newmethod () {list<integer> List = Arrays.aslist (1,2,3,4,5,6); List.foreach (New Consumer <Integer> () {@Overridepublic void accept (Integer t) {System.out.println (t);}});} public static void For_lambda () {list<integer> List = Arrays.aslist (1,2,3,4,5,6); List.foreach (i- System.out.println (i));}}

　　

The results of these three methods are the same after the last execution

In the For_newmethod method, you can see that the list has added a new method,forEach , to iterate over the elements, whose parameters are a consumer interface.

Consumer interface under the Java.util.function package, the package is a newly introduced toolkit java8, which has a @functionalinterface interface. /* Copyright (c), Oracle and/or its affiliates. All rights reserved. * ORACLE proprietary/confidential. Use are subject to license terms. */package Java.lang;import java.lang.annotation.*;/** * An informative annotation type used to indicate this an interface * Type declaration is intended to being a <i>functional interface</i> as * defined by the Java Language Specifica Tion.* This is a notification annotation type that is used to represent an interface declaration, which refers to a functional interface, which is defined by the Java language Specification. (That is, if an interface is added @functionalinterface,* the interface is a functional interface) * Conceptually, a functional interface has exactly one abstract * me  Thod.  Since {@linkplain java.lang.reflect.method#isdefault () * Default Methods} has an implementation, they is not abstract. IF * An interface declares a abstract method overriding one of the * public methods of {@code Java.lang.Object}, that Al So does * <em>not</em> count toward the interface ' s abstract method Count *Since any implementation of the interface would have a * implementation from {@code Java.lang.Object} or elsewhere. * Conceptually, a functional interface has only one abstract method, because the Java.lang.reflect.Method method Sdefault () has an implementation, and they are not abstract. If an interface declares a method of an interface and overrides a public method inside the Java.lang.Object class, then it does not count to the abstract method of the interface plus 1, * Because any implementation of an interface will have an implementation from the Java.lang.Object class or somewhere else. * <p>note that instances of functional interfaces can is created with * lambda expressions, method references, or CO Nstructor references. * Note that an instance of a digital interface can be created through a lambda expression, a method reference, or a construction method reference.  * <p>if a type is annotated with this annotation type, compilers be * required to generate an error message unless:  * If an annotation type is taken with this @functionalinterface, the compiler generates an error message unless the following are true: * <ul> * <li> The type is a interface type and not An annotation type, enum, or class. * <li> The annotated type satisfies the requirements of a functional interface.  * </ul> * This type is an interface type and is not an annotation, enumeration, or class type * The annotated type satisfies the requirements of the functional interface * <p>however, the compiler would treat any interface Meeting the * Definition of a functional interface as a functional interface * regardless of whether or not a {@code functionalinterf ACE} * Annotation is present on the interface declaration. * However, the compiler will treat Khur interfaces that satisfy the definition of a functional interface, and it will be treated as a functional interface regardless of whether the @functionalinterface annotation type is added to its declaration. * @jls 4.3.2. The Class Object * @jls 9.8 functional Interfaces * @jls 9.4.3 Interface Method Body * @since 1.8 */@Documented @retention ( Retentionpolicy.runtime) @Target (elementtype.type) public @interface Functionalinterface {}

put @FunctionalInterface (functional interface) of the document translated, or feel very around, and then summed up,

What is a functional interface:

1, the interface is added @FunctionalInterface, indicating that it is a functional interface.

2, if an interface has only one abstract method, then it is a functional interface.

3.If an interface has an abstract method and some method that overrides the public method of the Java.lang.Object class, it means that it is a functional interface.

Java 8 new Features 1-function interface