Java Variable Hiding: How Subclass Fields Mask Base Class Members

In Java, if a subclass declares a member variable with the same name as one in its superclass, the subclass variable hides the superclass variable—even when their data types differ; the hidden variable can only be accessed via the super keyword.

Example code illustrates this concept:

class Father{</code>
<code>    public Strings = "父类";</code>
<code>}</code>
<code>class Son extends Father{</code>
<code>    public String s = "子类";</code>
<code>}</code>
<code>public class SonTest{</code>
<code>    public static void main(String[] args){</code>
<code>        Son son = new Son();</code>
<code>        System.out.println(son.s);</code>
<code>    }</code>
<code>}

Running the program prints 子类, confirming that the Son class's s field hides the field with the same name in Father.

The author notes that, although the language permits such hiding, it is generally discouraged because it can make the code harder to read and maintain.