这和超级java

问题描述

此和超级关键字不是它们;那么我如何使用它们以与方法相同的方式将参数传递给构造函数？
简而言之，两者都能表现出如此明显的行为？

this and super are keywords aren't they; then how can I use them for passing arguments to constructors the same way as with a method??In short how is it that both can show such distinct behaviors??

推荐答案

你是正确的两个此和 super 是关键字。 明确定义了它们的行为方式。简短的回答是这些关键字的行为特别，因为规范说它们必须。

You are correct that both this and super are keywords. The Java language specification defines explicitly how they must behave. The short answer is that these keywords behave specially because the specification says that they must.

根据规范这个可以使用 （仅限某些地方）或。

According to the specification this can be used a primary expression (only in certain places) or in an explicit constructor invocation.

所以你可以使用这个作为函数的参数，以传递对当前对象的引用。但请注意，您不能使用 super ，就像它不是主表达式一样：

So you can use this as an argument to a function to pass a reference to the current object. However note that you cannot use super in the same way as it is not a primary expression:

public class Program
{   
    void test(Program p) {}

    void run() { test(super); }

    public static void main(String[] args)
    {
        new Program().run();
    }
}

结果：

Program.java:5: '.' expected
    void run() { test(super); }

你可以使用 super.foo 虽然因为这是在中定义的有效：

You can use super.foo though because this is defined in 15.11 to be valid:

FieldAccess:
    Primary . Identifier
    super . Identifier
    ClassName .super . Identifier

规范还放：

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