java - 面试题：请问，以下哪些修饰符可以使其修饰的变量只能对同包类或子类有效？

Question

如题这个答案正确吗？

package com;

public class TestParent {
    protected String protectedStr="protected";
    String defaultStr="default";

    private void method() {

    }
    void abm(){
        
    }

    protected void proabc(){
        
    }
}

package com;

public class TestSon extends TestParent{

    private void test(){
    
        
    }
}

package com;

class Main {

    static public void main(String[] args) {

        TestParent parent = new TestParent();
        TestSon son = new TestSon();
        parent.abm();//default method 
        son.abm();//default method 
        System.out.println(parent.protectedStr);
        System.out.println(parent.defaultStr);

        // -------------
        parent.proabc(); //protected method 
        son.proabc(); //protected method 
        System.out.println(son.protectedStr);
        System.out.println(son.defaultStr);

    }

}

Answer 1

作用域	當前類別	當前包	子孫類	其他包裝
public	√	√	√	√
protected	√	√	√	×
friendly	√	√	×	×
private	√	×	×	×

---

不寫預設就是 friendly.

選 C 沒毛病