why java allows it to compile?

Pls check the below code. It compiles, but it doesn't run.

I can understand that it cannot run.

But why java allows it to compile? It is obvious that this cannot run.

import java.util.*;

public class TrialClass {

public static void main (String args[])
{
    ParentClass parentObject = new ParentClass();
    ChildClass childObject = new ChildClass();
    
    childObject = (ChildClass)parentObject;
    
    childObject.inheritMethod();
}


}

class ParentClass
{
    protected void inheritMethod()
    {
        System.out.println("from Parent class");
    }
}

class ChildClass extends ParentClass
{
    protected void inheritMethod()
    {
        System.out.println("from Child class");
    }
}

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