为什么System.out.println必须在方法内？ [英] Why does System.out.println have to be inside a method?

问题描述

class Employee {    
    int DOB;
    int eid;
    String name;
    double salary;
    System.out.println("Employee class");
}

如果我写 System.out.println 在一个方法里面，它似乎工作。但不是直接写在一个类中。为什么是一个方法需要

If I write the System.out.println inside a method,it seems to work. But not when written directly inside a class. Why is a method necessary?

推荐答案

这是一样的被执行任何其他代码 - 它必须是一个方法里面！ （是的，ISH，对于较真的，我还包括构造函数和静态/实例初始化器块。）想想看 - 如果它不是一个方法或者你提出其他相关的代码块内，那么当将这些代码得到执行？这没有多大意义。你不能执行一个类本身，你只能执行该类中包含的特定方法/构造函数等。

It's the same as any other code that gets executed - it has to be inside a method! (Yes, ish, for the purists, I'm also including constructors and static / instance initialiser blocks.) Think about it - if it wasn't inside a method or other related code block as you propose, then when would that code get executed? It wouldn't make much sense. You can't execute a class per-se, you can only execute a specific method / constructor / etc. contained within that class.

外部方法和构造函数声明允许的唯一事物是字段的声明。由于 System.out.println（）不是字段声明，因此不允许。

The only things allowed outside method and constructor declarations are declarations of fields. Since System.out.println() is not a field declaration, it's not allowed.

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