Why is IntelliJ telling me this variable has not been initialized?

问题

I am working on a class with an inner class

My code:

package com.solignis;
public class Config {
    public static final Target target;
    class Target {
        public void create(String targetName) {    
            System.out.println("Created" + targetName);   
        }

        public void destroy(String targetName) {    
            System.out.println("Destroyed" + targetName);    
        }
    }    
}

IntelliJ doesn't see anything wrong with the subclass but it keeps complaining that I have not initalized the static variable target. But when I try to initialize it with something like null I get a null pointer exception (no surprise there!) but I don't what I could initialize the variable with since as far I can understand all its just an instance of the Target subclass in the Example superclass (is this right?). Also Target has no constructor so I cannot declare new on target in order to initialize the variable.

So what could I do?

Please correct me if I am incorrect about my understanding of this I am still trying to wrap my head around the more "deeper" workings of Java.

回答1:

The variable test is indeed not initialized: public static Test test;

Initialization means putting value into the variable, i.e. something like this: test = SOMETHING;

The SOMETHING may be either null or an instance of the type of the variable. In your case:

test = null;
test = new Test();

are valid expressions.

Indeed if you put null to the test you cannot "use" it, i.e. invoke its method or access its member variables.

BTW. Test is not a subclass of Example as probably you think. It is its inner class. Subclass is a class that extends other class. Actually Test is a direct subclass of object.

回答2:

in fact you can initialize a class that you do not declared a constructor for it it has a default constructor with no argument

    test = new Test();

来源：https://stackoverflow.com/questions/16747456/why-is-intellij-telling-me-this-variable-has-not-been-initialized