New feature of java8-functional interface
Function interface: an interface and an abstract method constitute a functional interface, which can be annotated @FunctionalInterface
Specify the constraint that the interface is a functional interface; a functional interface can only have one abstract method of its own
Simple to use:
Custom function interface: Three function interfaces are defined
package com.xiaodu.java8.methodcite;
import java.util.function.Supplier;
/**
* 定义函数接口
* @author 84287
*
*/
public interface FunctionInterface {
/*
* 获取类的实例
*/
@FunctionalInterface
interface function01<T>{
T getObject();
}
//函数接口是主要是给Lambda使用 java8中已经有好多函数接口，很多不用自己定义
//本人自己定义的function01<t> 其实和 java.util.function中的Supplier<T>一样的
}
Use function interface:
public static void main(String[] args) {
function01<String> f01 = () -> "xiaoming";
String string = f01.getObject();
System.out.println(string.length()); // 8
}Complete list of function interfaces included in java 8:
Functional interfaces that existed before JDK 1.8:
· 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
---------------------
Function interface under java.util.function.*
| Serial number | Interface name && abstract method | Remarks |
|---|---|---|
| 1 | BiConsumer<T,U> ； void accept(T t, U u); |
Represents an operation that accepts two input parameters and does not return any results |
| 2 | BiFunction<T,U,R>； R apply(T t, U u); |
Represents a method that accepts two input parameters and returns a result |
| 3 | BinaryOperator<T>； 继承BiFunction<T,U,R>； |
Represents an operation that acts on two operators of the same type, and returns the result of the same type of operator |
| 4 | BiPredicate<T,U>； boolean test(T t, U u); |
Represents a two-parameter return boolean value method |
| 5 | BooleanSupplier | Represents the provider of the boolean value result |
| 6 |
Consumer<T>； void accept(T t); |
Represents an operation that accepts an input parameter and does not return |
| 7 | DoubleBinaryOperator； double applyAsDouble(double left, double right); |
Represents the operation of two double value operators, and returns a double value result |
| 8 | DoubleConsumer； void accept(double value); |
Represents an operation that accepts a double value parameter and does not return a result |
| 9 | DoubleFunction<R>； R apply(double value); |
Represents a method that accepts a double value parameter and returns the result |
| 10 | DoublePredicate； boolean test(double value); |
Represents a boolean return method with a double value parameter |
| 11 | DoubleSupplier； double getAsDouble(); |
Represents a method that returns a double value without parameters |
| 12 | DoubleToIntFunction； int applyAsInt(double value); |
Accept a double type input and return an int type result |
| 13 | DoubleToLongFunction； long applyAsLong(double value); |
Accept a double type input and return a long type result |
| 14 | DoubleUnaryOperator； double applyAsDouble(double operand); |
Accepts a parameter of the same type double, and the return value type is also double. |
| 15 | Function<T,R>； R apply(T t); |
接受一个输入参数，返回一个结果 |
| 16 | IntBinaryOperator； int applyAsInt(int left, int right); |
接受两个参数同为类型int,返回值类型也为int |
| 17 | IntConsumer； void accept(int value); |
接受一个int类型的输入参数，无返回值 |
| 18 | IntFunction<R>； R apply(int value); |
接受一个int类型输入参数，返回一个结果 |
| 19 | IntPredicate； boolean test(int value); |
接受一个int输入参数，返回一个布尔值的结果 |
| 20 | IntSupplier； int getAsInt(); |
无参数，返回一个int类型结果 |
| 21 | IntToDoubleFunction； double applyAsDouble(int value); |
接受一个int类型输入，返回一个double类型结果 |
| 22 | IntToLongFunction； long applyAsLong(int value); |
接受一个int类型输入，返回一个long类型结果 |
| 23 | IntUnaryOperator； int applyAsInt(int operand); |
接受一个参数同为类型int,返回值类型也为int |
| 24 | LongBinaryOperator； long applyAsLong(long left, long right); |
接受两个参数同为类型long,返回值类型也为long |
| 25 | LongConsumer； void accept(long value); |
接受一个long类型的输入参数，无返回值 |
| 26 | LongFunction<R>； void accept(long value); |
接受一个long类型输入参数，返回一个结果 |
| 27 | LongPredicate； boolean test(long value); |
接受一个long输入参数，返回一个布尔值类型结果 |
| 28 | LongSupplier； long getAsLong(); |
无参数，返回一个结果long类型的值 |
| 29 | LongToDoubleFunction； double applyAsDouble(long value); |
接受一个long类型输入，返回一个double类型结果 |
| 30 | LongToIntFunction； int applyAsInt(long value); |
接受一个long类型输入，返回一个int类型结果 |
| 31 | LongUnaryOperator； long applyAsLong(long operand); |
接受一个参数同为类型long,返回值类型也为long |
| 32 | ObjDoubleConsumer<T>； void accept(T t, double value); |
接受一个object类型和一个double类型的输入参数，无返回值 |
| 33 | ObjIntConsumer<T>； void accept(T t, int value); |
接受一个object类型和一个int类型的输入参数，无返回值 |
| 34 | ObjLongConsumer<T>； void accept(T t, long value); |
接受一个object类型和一个long类型的输入参数，无返回值 |
| 35 | Predicate<T>； boolean test(T t); |
接受一个输入参数，返回一个布尔值结果 |
| 36 | Supplier<T>； T get(); |
无参数，返回一个结果 |
| 37 | ToDoubleBiFunction<T,U>； double applyAsDouble(T t, U u); |
接受两个输入参数，返回一个double类型结果 |
| 38 | ToDoubleFunction<T>； double applyAsDouble(T value); |
接受一个输入参数，返回一个double类型结果 |
| 39 | ToIntBiFunction<T,U>； int applyAsInt (T t, U u); |
Accepts two input parameters and returns an int type result |
| 40 | ToIntFunction<T>； int applyAsInt(T value); |
Accepts an input parameter and returns an int type result |
| 41 | ToLongBiFunction<T,U>； long applyAsLong(T t, U u); |
Accepts two input parameters and returns a long type result. |
| 42 | ToLongFunction<T>； long applyAsLong(T value); |
Accepts an input parameter and returns a long type result |
| 43 | UnaryOperator<T>； 继承： extends Function<T, T>； R apply(T t); |
Accepts a parameter of type T, and the return value type is also T |
| 44 | The above is the functional interface after java8 |
|
Simply use the function interface that comes with java8
The code reflects:
Use the functional interface that comes with java8
public static void main(String[] args) {
String string = MethodCiteFunction.supplier(() -> "接受一个空参，返回一个String对象");
System.out.println(string);
// 空参，返回一个person对象
Person person = MethodCiteFunction.supplier(() -> new Person());
// 方法引用，空参返回一个person对象
Person person2 = MethodCiteFunction.supplier(Person::new);
}
/**
* Supplier<T> 无参，返回一个泛型类型的对象
* @param supplier
* @return
*/
public static <T>T supplier(Supplier<T> supplier) {
return supplier.get();
}