为什么从 main 中读取非静态变量会出现问题? [英] Why is there a problem with a non-static variable being read from main?

问题描述

String name = "Marcus";
static String s_name = "Peter";

public static void main(String[] args) {    
    System.out.println(name);//ERROR
    System.out.println(s_name);//OK
}

错误:无法对非静态字段名称进行静态引用

ERROR: Cannot make a static reference to the non-static field name

推荐答案

导致这个问题的原因是 main 是一个静态方法，这意味着它没有接收器对象.换句话说，它不会相对于某个对象进行操作.因此，如果您尝试查找非静态字段，那么 Java 会混淆该字段所在的对象.通常，它会假设该字段位于调用方法的对象中，但是因为 main 是静态的，这个对象不存在.

The reason this causes a problem is that main is a static method, which means that it has no receiver object. In other words, it doesn't operate relative to some object. Consequently, if you try looking up a non-static field, then Java gets confused about which object that field lives in. Normally, it would assume the field is in the object from which the method is being invoked, but because main is static this object doesn't exist.

作为一般规则，您不能从静态方法访问常规实例变量.

As a general rule, you cannot access regular instance variables from static methods.

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