JAVA8学习笔记-function

2023年9月26日 136次阅读 来源: 吃水煮鱼片

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

定制化自己的consumer–ThiConsumer

处理三个参数

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

        default ThiConsumer<T,U,W> andThen(ThiConsumer<? super 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<T,U> Consumer<T> DoubleConsumer IntConsumer LongConsumer ObjDoubleConsumer<T> ObjIntConsumer<T> ObjLongConsumer<T> */

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

        default ThiConsumer<T,U,W> andThen(ThiConsumer<? super T,? super U,? super W> 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 <V> BiFunction<T, U, V> andThen(Function<? super R, ? extends V> 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<R>
//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<R>
IntToDoubleFunction
IntToLongFunction
IntUnaryOperator
LongBinaryOperator
LongFunction<R>
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<T,U,R> BinaryOperator<T> DoubleBinaryOperator DoubleFunction<R> DoubleToIntFunction DoubleToLongFunction DoubleUnaryOperator Function<T,R> IntBinaryOperator IntFunction<R> IntToDoubleFunction IntToLongFunction IntUnaryOperator LongBinaryOperator LongFunction<R> LongToDoubleFunction LongToIntFunction LongUnaryOperator ToDoubleBiFunction<T,U> ToDoubleFunction<T> ToIntBiFunction<T,U> ToIntFunction<T> ToLongBiFunction<T,U> ToLongFunction<T> UnaryOperator<T> * @param args */
    public static void main(String[] args) {
        BiFunction<T, U, R> 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<R, W> 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<T> 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>
    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)BooleanSupplierDoubleSupplier,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		BiPredicateBiFunction
BinaryOperator
DoubleBinaryOperator
IntBinaryOperator
LongBinaryOperator
ToDoubleBiFunction
ToIntBiFunction
ToLongBiFunction

附件

java8 api 下载链接

    原文作者：吃水煮鱼片
    原文地址: https://blog.csdn.net/weixin_29135773/article/details/54095573
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