java protected

package project_demo.p1;

public class Father {
    protected void f(){}
}

package project_demo.p1;

public class Son1 extends Father{

    public Son1() throws CloneNotSupportedException {
        clone();
    }
}

package project_demo.p2;

import project_demo.p1.Father;

public class Son2 extends Father {
}

注意：Father的clone方法来自于Object类，该方法的可见性为java.lang包和Object类的Father子类，对于Son1、Son2类不可见