在子类中访问超类静态变量

Question

I have a superclass Test with a static variable a and I've also created a subclass Test1 from which I am able to access superclass static variable.

Is this a valid way to do so? Any explanation is highly appreciated.

public class Test {

    public static String a = "";

    Test() {
        a += "testadd";
    }
}

public class Test1 extends Test {

    public Test1() {
        a += "test1add";
    }

    public static void main(String args[]){
        Test1 test1 = new Test1();
        System.out.println(a);
    }
}

Answer 1

Static variables are class variables, you can access them using classname.variablename.

public class Test {

    public static String a = "";

    Test() {
        a += "testadd";
    }
}

public class Test1 extends Test {

    public Test1() {
        Test.a += "test1add";
    }

    public static void main(String args[]) {
        Test1 test1 = new Test1();
        System.out.println(a);
    }
}

Answer 2

You can access it using the subclass object.superClassStaticField or SuperClassName.superClassStaticField . Latter is the static way to access a static variable.

For example:

public class SuperClassStaticVariable {
    public static void main(String[] args) {
        B b = new B();
        b.a = 2; // works but compiler warning that it should be accessed as static way
        A.a = 2; // ok 
    }
}

class A {   
    static int a;
}
class B extends A {}