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Java8 Supplier接口和Consumer接口原理解析

2023-07-26 12:41:07 344

Supplier接口

packagejava.util.function;
/**
*Representsasupplierofresults.
*
*Thereisnorequirementthatanewordistinctresultbereturnedeach
*timethesupplierisinvoked.
*
*
Thisisafunctionalinterface
*whosefunctionalmethodis{@link#get()}.
*
*@paramthetypeofresultssuppliedbythissupplier
*
*@since1.8
*/
@FunctionalInterface
publicinterfaceSupplier{
/**
*Getsaresult.
*
*@returnaresult
*/
Tget();
}

supplier接口只有一个抽象方法get(),通过get方法产生一个T类型实例。

实例：

packageme.yanand;
importjava.util.function.Supplier;
publicclassTestSupplier{
publicstaticvoidmain(String[]args){
SupplierappleSupplier=Apple::new;
System.out.println("--------");
appleSupplier.get();
}
}
classApple{
publicApple(){
System.out.println("创建实例");
}
}

Consumer接口

packagejava.util.function;
importjava.util.Objects;
/**
*Representsanoperationthatacceptsasingleinputargumentandreturnsno
*result.Unlikemostotherfunctionalinterfaces,{@codeConsumer}isexpected
*tooperateviaside-effects.
*
*Thisisafunctionalinterface
*whosefunctionalmethodis{@link#accept(Object)}.
*
*@paramthetypeoftheinputtotheoperation
*
*@since1.8
*/
@FunctionalInterface
publicinterfaceConsumer{
/**
*Performsthisoperationonthegivenargument.
*
*@paramttheinputargument
*/
voidaccept(Tt);
/**
*Returnsacomposed{@codeConsumer}thatperforms,insequence,this
*operationfollowedbythe{@codeafter}operation.Ifperformingeither
*operationthrowsanexception,itisrelayedtothecallerofthe
*composedoperation.Ifperformingthisoperationthrowsanexception,
*the{@codeafter}operationwillnotbeperformed.
*
*@paramaftertheoperationtoperformafterthisoperation
*@returnacomposed{@codeConsumer}thatperformsinsequencethis
*operationfollowedbythe{@codeafter}operation
*@throwsNullPointerExceptionif{@codeafter}isnull
*/
defaultConsumerandThen(Consumerafter){
Objects.requireNonNull(after);
return(Tt)->{accept(t);after.accept(t);};
}
}

一个抽象方法accept(Tt)定义了要执行的具体操作；注意看andThen方法，接收Consumer类型参数，返回一个lambda表达式，此表达式定义了新的执行过程，先执行当前Consumer实例的accept方法，再执行入参传进来的Consumer实例的accept方法，这两个accept方法接收都是相同的入参t。

实例：

packageme.yanand;
importjava.util.function.Consumer;
publicclassTestConsumer{
publicstaticvoidmain(String[]args){
Consumerconsumer=(t)->{
System.out.println(t*3);
};
ConsumerconsumerAfter=(s)->{
System.out.println("之后执行："+s);
};
consumer.andThen(consumerAfter).accept(5);
}
}

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Java8 Supplier接口和Consumer接口原理解析

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