Why Does Java's Static Variable Inheritance Produce Unexpected Results?

Java Class Variable Override Conundrum

Consider the following Java code snippet:

<br>class Dad {</p>
<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">protected static String me = "dad";

public void printMe() {
    System.out.println(me);
}

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}

class Son extends Dad {

protected static String me = "son";

}

public void doIt() {

new Son().printMe();

}

The code appears to define a class variable named "me" in both the "Dad" and "Son" classes. When calling "doIt()", one might expect the code to print "son" since "Son" is a subclass of "Dad". However, this is not what happens.

Why Does "doIt()" Print "dad"?

In Java, class variables cannot be overridden. Instead, they are hidden. Specifically, when declaring a class variable with an existing name in a subclass, the subclass hides the inherited class variable, effectively creating a new class variable with the same name but distinct from its parent class.

Overriding vs. Hiding

Overriding involves providing a different implementation for a method in a subclass that overrides the method in the superclass. In contrast, hiding involves using the same variable name in a subclass, but it hides the variable inherited from the superclass and creates a new variable local to the subclass.

How to Print "son"?

To achieve the desired behavior of printing "son", one cannot override the class variable. Instead, one can use other inheritance techniques such as:

• Using a different variable name in the subclass, e.g., "myName" instead of "me".
• Modifying the inherited class variable using reflection (this method is not recommended for general use).
• Passing the value as a constructor argument, as shown in the example below:

Example with Constructor Argument:

<br>public class Person {</p>
<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">private String name;

public Person(String name) {
    this.name = name;
}

public void printName() {
    System.out.println(name);
}

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