Java 8 new Features-Rookie tutorial (3)-java 8 function interface

Java 8 Functional Interface

A functional interface (functional Interface) is an interface that has and has only one abstract method, but can have multiple non-abstract methods.

A functional interface can be implicitly converted to a lambda expression.

A functional interface can support lambda in an existing function-friendly manner.

Pre-JDK 1.8 functional Interfaces:

• Java.lang.Runnable
• Java.util.concurrent.Callable
• Java.security.PrivilegedAction
• Java.util.Comparator
• Java.io.FileFilter
• Java.nio.file.PathMatcher
• Java.lang.reflect.InvocationHandler
• Java.beans.PropertyChangeListener
• Java.awt.event.ActionListener
• Javax.swing.event.ChangeListener

New added function interface for JDK 1.8:

• Java.util.function

Java.util.function it contains a number of classes that are used to support functional programming in Java, the function interface in the package is:

Serial Number	Interface & Description
1	Biconsumer<t,u>: represents an operation that accepts two input parameters and does not return any results
2	Bifunction<t,u,r>: represents a method that accepts two input parameters and returns a result
3	Binaryoperator<t>: represents an operation that acts on two homogeneous operators, and returns the result of the same type of operator
4	Bipredicate<t,u>: A Boolean method that represents a two-parameter
5	Booleansupplier: A provider that represents the result of a Boolean value
6	Consumer<t>: represents an operation that takes an input parameter and has no return
7	Doublebinaryoperator: represents an operation that acts on a two double value operator and returns the result of a double value.
8	Doubleconsumer: represents an operation that accepts a double value parameter and does not return a result.
9	Doublefunction<r>: represents a method that accepts a double value parameter and returns the result
10	Doublepredicate: Represents a Boolean value method that has a double value argument
11	Doublesupplier: represents a provider of a double value structure
12	doubletointfunction: accepts a double type input and returns an int type result.
13	doubletolongfunction: accepts a double type input, returns a long type result
14	Doubleunaryoperator: accepts a parameter of the same type double, and the return value type is also double.
15	Function<t,r>: accepts an input parameter and returns a result.
16	Intbinaryoperator: accepts two parameters of the same type int, and the return value type is also int.
17	Intconsumer: accepts an input parameter of type int, no return value.
18	Intfunction<r>: accepts an int type input parameter and returns a result.
19	intpredicate: takes an int input parameter and returns the result of a Boolean value.
20	intsupplier: No parameter, returns an int type result.
21st	inttodoublefunction: accepts an int type input and returns a double type result.
22	inttolongfunction: accepts an int type input and returns a long type result.
23	Intunaryoperator: accepts a parameter of the same type int, and the return value type is also int.
24	Longbinaryoperator: accepts two parameters of the same type long, and the return value type is also long.
25	Longconsumer: accepts a long type of input parameter with no return value.
26	Longfunction<r>: accepts a long type input parameter and returns a result.
27	longpredicate: R takes a long input parameter and returns a Boolean value type result.
28	longsupplier: No parameter, returns a result long type value.
29	longtodoublefunction: accepts a long type input and returns a double type result.
30	longtointfunction: accepts a long type input and returns an int type result.
31	Longunaryoperator: accepts a parameter of the same type long, and the return value type is also long.
32	Objdoubleconsumer<t>: accepts an object type and an input parameter of type double, no return value.
33	Objintconsumer<t>: accepts an object type and an input parameter of type int, no return value.
34	Objlongconsumer<t>: accepts an object type and an input parameter of type long, no return value.
35	Predicate<t>: accepts an input parameter and returns a Boolean result.
36	supplier<t>: no parameter, returns a result.
37	Todoublebifunction<t,u>: accepts two input parameters, returns a double type result
38	Todoublefunction<t>: accepts an input parameter and returns a double type result
39	Tointbifunction<t,u>: accepts two input parameters and returns an int type result.
40	Tointfunction<t>: accepts an input parameter and returns an int type result.
41	Tolongbifunction<t,u>: accepts two input parameters, returns a long type result.
42	Tolongfunction<t>: accepts an input parameter and returns a long type result.
43	Unaryoperator<t>: accepts a parameter of type T, and the return value type is also T.

Functional Interface Instances

1.Predicate

 PackageJava8.cainiao;Importjava.util.Arrays;Importjava.util.List;Importjava.util.function.Predicate; Public classPredicatetest { Public Static voidMain (String args[]) {List<Integer> list = Arrays.aslist (1, 2, 3, 4, 5, 6, 7, 8, 9); //predicate<integer> predicate = n-True//N is a test method that passes a parameter to the predicate interface//N If present, the test method returns TrueSystem.out.println ("Output All data:"); //Pass parameter nEval (list, n->true); //predicate<integer> predicate1 = n-n%2 = = 0//N is a test method that passes a parameter to the predicate interface//returns True if n%2 is 0 test methodSystem.out.println ("Output all even numbers:"); eval (list, nn%2 = = 0 ); //predicate<integer> predicate2 = n > 3//N is a test method that passes a parameter to the predicate interface//if n is greater than 3 the test method returns TrueSYSTEM.OUT.PRINTLN ("Output all numbers greater than 3:"); eval (list, nn > 3 ); }        Public Static voidEval (list<integer> List, predicate<integer>predicate) {       for(Integer n:list) {if(Predicate.test (n)) {System.out.println (n+ " "); }      }   }}

Java 8 new Features-Rookie tutorial (3)-java 8 function interface