JAVA8学习笔记-function

JAVA8学习笔记-Function

Consumer

类和方法说明

Consumer接口主要是处理参数不提供返回结果的函数式接口
java自带的api提供的实现接口

//接受2种类型的参数,进行处理
BiConsumer
    void accept(T t, U u);
    default BiConsumer andThen(BiConsumersuper T, ? super U> after);
//接受单个参数,进行处理
Consumer
    void accept(T t);
     default Consumer andThen(Consumersuper T> after);
//接受double类型的参数,进行处理
DoubleConsumer
    void accept(double value);
    default DoubleConsumer andThen(DoubleConsumer after);
//接受int类型的参数,进行处理
IntConsumer
    void accept(int value);
    default IntConsumer andThen(IntConsumer after);
//接受long类型的参数,进行处理
LongConsumer
    void accept(long value);
    default LongConsumer andThen(LongConsumer after);
//接受T和double类型的参数,进行处理
ObjDoubleConsumer
    void accept(T t, double value);
//接受T和int类型的参数,进行处理
ObjIntConsumer
     void accept(T t, int value);
//接受T和long类型的参数,进行处理
ObjLongConsumer
     void accept(T t, long value);

定制化自己的consumer–ThiConsumer

处理三个参数

@FunctionalInterface
    static interface ThiConsumer{
        void accept(T t, U u, W w);

        default ThiConsumer andThen(ThiConsumersuper T,? super U,? super W> consumer){
            return (t, u, w)->{
                accept(t, u, w);
                consumer.accept(t, u, w);
            };
        }
    }

演示代码

import java.util.function.BiConsumer;
import java.util.function.Consumer;
import java.util.function.DoubleConsumer;
import java.util.function.IntConsumer;
import java.util.function.LongConsumer;
import java.util.function.ObjDoubleConsumer;
import java.util.function.ObjIntConsumer;
import java.util.function.ObjLongConsumer;

public class ConsumerDemo {
    /*BiConsumer
    Consumer
    DoubleConsumer
    IntConsumer
    LongConsumer
    ObjDoubleConsumer
    ObjIntConsumer
    ObjLongConsumer
*/

    public static void main(String[] args) throws Exception {
        System.out.println("------show biConsumer------");
        BiConsumer biConsumer = (T t, U u)->{System.out.println(String.format("biConsumer receive-->%s+%s", t,u));};
        BiConsumer biConsumer2 = (T t, U u)->{System.out.println(String.format("biConsumer2 receive-->%s+%s", t,u));};

        biConsumer.andThen(biConsumer2).accept(new T(), new U());


        System.out.println("------show consumer------");
        Consumer consumer = (T t)->{System.out.println(String.format("consumer receive-->%s", t));};
        Consumer consumer2 = (T t)->{System.out.println(String.format("consumer2 receive-->%s", t));};
        consumer.andThen(consumer2).accept(new T());

        System.out.println("------show doubleConsumer------");
        DoubleConsumer doubleConsumer = (d)->{System.out.println(String.format("doubleConsumer receive-->%s", d));};
        doubleConsumer.accept(100_111.111_001d);

        System.out.println("------show intConsumer------");
        IntConsumer intConsumer = (i)->{System.out.println(String.format("doubleConsumer receive-->%s", i));};
        intConsumer.accept(1_111);

        System.out.println("------show longConsumer------");
        LongConsumer longConsumer = (l)->{System.out.println(String.format("longConsumer receive-->%s", l));};
        longConsumer.accept(111_111_111_111L);

        System.out.println("------show longConsumer------");
        ObjDoubleConsumer objDoubleConsumer = (T t, double d)->{System.out.println(String.format("objDoubleConsumer receive-->%s+%s", t,d));};
        objDoubleConsumer.accept(new T(), 100_111.111_001d);

        System.out.println("------show objIntConsumer------");
        ObjIntConsumer objIntConsumer = (T t, int i)->{System.out.println(String.format("objIntConsumer receive-->%s+%s", t,i));};
        objIntConsumer.accept(new T(), 1_111);

        System.out.println("------show objLongConsumer------");
        ObjLongConsumer objLongConsumer = (T t, long l)->{System.out.println(String.format("objLongConsumer receive-->%s+%s", t,l));};
        objLongConsumer.accept(new T(), 111_111_111_111L);


        System.out.println("------show biConsumer------");
        ThiConsumer thiConsumer = (T t, U u, W w)->{System.out.println(String.format("thiConsumer receive-->%s+%s+%s", t,u, w));};
        ThiConsumer thiConsumer2 = (T t, U u, W w)->{System.out.println(String.format("thiConsumer2 receive-->%s+%s+%s", t,u, w));};

        thiConsumer.andThen(thiConsumer2).accept(new T(), new U(), new W());
    }

    @FunctionalInterface
    static interface ThiConsumer{
        void accept(T t, U u, W w);

        default ThiConsumer andThen(ThiConsumer consumer){
            return (t, u, w)->{
                accept(t, u, w);
                consumer.accept(t, u, w);
            };
        }
    }

    static class T{
        @Override
        public String toString() {
            return "T";
        }
    }
    static class U{
        @Override
        public String toString() {
            return "U";
        }
    }
    static class W{
        @Override
        public String toString() {
            return "W";
        }
    }
    static class R{
        @Override
        public String toString() {
            return "R";
        }
    }


}

输出结果

------show biConsumer------
biConsumer receive-->T+U
biConsumer2 receive-->T+U
------show consumer------
consumer receive-->T
consumer2 receive-->T
------show doubleConsumer------
doubleConsumer receive-->100111.111001
------show intConsumer------
doubleConsumer receive-->1111
------show longConsumer------
longConsumer receive-->111111111111
------show longConsumer------
objDoubleConsumer receive-->T+100111.111001
------show objIntConsumer------
objIntConsumer receive-->T+1111
------show objLongConsumer------
objLongConsumer receive-->T+111111111111
------show biConsumer------
thiConsumer receive-->T+U+W
thiConsumer2 receive-->T+U+W

Function

类和方法说明

接受一定数量的参数 同时提供一个返回结果

//接受两种类型(T,U)的参数,返回R类型的结果
BiFunction<T,U,R>
    R apply(T t, U u);
    default  BiFunction<T, U, V> andThen(Function after);
//接受2个T类型的参数,返回T类型的结果
BinaryOperator<T>
//接受2个double类型的参数,返回double类型的结果
DoubleBinaryOperator
//接受double类型的参数,返回T类型的结果
DoubleFunction
//接受double类型的参数,返回int类型的结果
DoubleToIntFunction
//接受double类型的参数,返回long类型的结果
DoubleToLongFunction
//接受double类型的参数,返回double类型的结果
DoubleUnaryOperator
//接受T类型的参数,返回R类型的结果
Function<T,R>
//接受2个int类型的参数,返回int类型的结果
IntBinaryOperator
//接受2个int类型的参数,返回R类型的结果
IntFunction
IntToDoubleFunction
IntToLongFunction
IntUnaryOperator
LongBinaryOperator
LongFunction
LongToDoubleFunction
LongToIntFunction
LongUnaryOperator
//接受两种类型(T,U)的参数,返回double类型的结果
ToDoubleBiFunction<T,U>
//接受T类型的参数,返回double类型的结果
ToDoubleFunction<T>
ToIntBiFunction<T,U>
ToIntFunction<T>
ToLongBiFunction<T,U>
ToLongFunction<T>
//接受T类型的参数,返回T类型的结果
UnaryOperator<T>

演示代码

import java.util.Random;
import java.util.function.BiFunction;
import java.util.function.BinaryOperator;
import java.util.function.Function;


public class FunctionDemo {
/**
 * BiFunction
BinaryOperator
DoubleBinaryOperator
DoubleFunction
DoubleToIntFunction
DoubleToLongFunction
DoubleUnaryOperator
Function
IntBinaryOperator
IntFunction
IntToDoubleFunction
IntToLongFunction
IntUnaryOperator
LongBinaryOperator
LongFunction
LongToDoubleFunction
LongToIntFunction
LongUnaryOperator
ToDoubleBiFunction
ToDoubleFunction
ToIntBiFunction
ToIntFunction
ToLongBiFunction
ToLongFunction
UnaryOperator
 * @param args
 */
    public static void main(String[] args) {
        BiFunction biFunction = (T t, U u) -> {
            System.out.println(String
                    .format("biConsumer receive-->%s+%s", t, u));
            return new R();
        };
        biFunction.apply(new T(), new U());

        Function function = (R r)->{System.out.println(String
                .format("function receive-->%s", r));
        return new W();};

        W w = biFunction.andThen(function).apply(new T(), new U());
        System.out.println(w);

        BinaryOperator binaryOperator = (T t1, T t2)->{
            System.out.println(String
                    .format("binaryOperator receive-->%s+%s", t1, t2));
            return new Random().nextInt(10)>=5?t2:t1;};

        T tr = binaryOperator.apply(new T(), new T());
        System.out.println(tr);
    }

    static class T{
        @Override
        public String toString() {
            return "T";
        }
    }
    static class U{
        @Override
        public String toString() {
            return "U";
        }
    }
    static class W{
        @Override
        public String toString() {
            return "W";
        }
    }
    static class R{
        @Override
        public String toString() {
            return "R";
        }
    }
}

输出结果

biConsumer receive-->T+U
biConsumer receive-->T+U
function receive-->R
W
binaryOperator receive-->T+T
T

Predicate

类和方法说明

相当于是Function的特殊形式 返回结果是boolean类型

提供一定形式的boolean运算

BiPredicate<T,U>
DoublePredicate
IntPredicate
LongPredicate
Predicate<T>

Supplier

类和方法说明

不提供参数,获取一种类型的返回结果

BooleanSupplier
DoubleSupplier
IntSupplier
LongSupplier
##获取一个T类型的实例
Supplier
    T get();

---

总结

从上面的方法列表可以看出,Consumer,Function,Predicate,Supplier的差别在于提供的参数和返回结果

	无返回结果	返回boolean结果	返回其他类型结果
不提供参数	()->{};(runable实现等)	BooleanSupplier	DoubleSupplier,IntSupplier,LongSupplier,Supplier
提供一个参数	Consumer DoubleConsumer IntConsumer LongConsumer	DoublePredicate IntPredicate LongPredicate Predicate	DoubleFunction DoubleToIntFunction DoubleToLongFunction DoubleUnaryOperator Function IntFunction IntToDoubleFunction IntToLongFunction IntUnaryOperator LongFunction LongToDoubleFunction LongToIntFunction LongUnaryOperator ToDoubleFunction ToIntFunction ToLongFunction UnaryOperator
提供两个参数	BiConsumer ObjDoubleConsumer ObjIntConsumer ObjLongConsumer	BiPredicate	BiFunction BinaryOperator DoubleBinaryOperator IntBinaryOperator LongBinaryOperator ToDoubleBiFunction ToIntBiFunction ToLongBiFunction

附件

java8 api 下载链接