An example:

import java.util.*;

public class JavaPolymorph 
{
    public void Print()
    { System.out.println( "JavaPolymorph"); }  
    
   public static void main(String[] args)
   {
      JavaPolymorph j1 = new JavaPolymorph(); 
      JavaPolymorph j2 = new SubJavaPolymorph();
      
      j1.Print();
      j2.Print();       
   }
}

public class SubJavaPolymorph extends JavaPolymorph
{
    public void Print()
    { System.out.println( "SubJavaPolymorph"); }    
}

Giving the output:

JavaPolymorph
SubJavaPolymorph