Java泛型方法签名说明 [英] Java generics method signature explanation

问题描述

此通用方法签名是什么意思

What does this generic method signature means

public <S, D> D map(S sourceObject, java.lang.Class<D> destinationClass);

我指的是<S, D>.
此方法返回与第二个参数中发送的对象相同类型的对象.

I am referring to the <S, D>.
This method returns an object of the same type that was sent in the second parameter.

我不能只写

public D map(S sourceObject, java.lang.Class<D> destinationClass);

推荐答案

这意味着该方法调用采用两个类型参数:S和D.

That means that this method invocation takes two type parameters: S and D.

<S, D>部分是为了声明此方法是通用的，并接受两个类型参数，然后将它们用作方法签名中实际类型的占位符.

The <S, D> part is meant as a declaration that this method is generic and takes two type parameters which are then used as placeholders for actual types in the method signature.

调用该方法时，要么提供参数，要么从您作为参数传递的表达式类型中推断出参数，如下所示:

When you invoke the method, either you supply the parameters or they get inferred from the types of the expressions you are passing as arguments, like this:

String val = map(10, String.class);

在这种情况下，S为Integer，D为String

In this case S is Integer and D is String

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