JAVA 多态

package peoplePack;

public class JavaApp {
    public static void main(String[] args) {
        Young y = new Young();
        y.testInstanceMethod();
        
        People p = new Young();
        p.testInstanceMethod();
        
        People.testClassMethod();
        Young.testClassMethod();
    }
}

class People {
    public static void testClassMethod(){
        System.out.println("Static Method in People");
    }
    
    public void testInstanceMethod(){
        System.out.println("Instance Method in People");
    }
}

class Young extends People{
    public static void testClassMethod(){
        System.out.println("The static method in Young");
    }
    
    public void testInstanceMethod(){
        System.out.println("The instance method in Young");
    }
}