checked exception issues in method overriding Examples

Demo1:
// super class method throws unchecked exception
// sub class method no throws
package oops;

class Parentclass
{
    public void sm()throws Exception
    {
    System.out.println("super class");
    }
}  
public class OREx extends Parentclass{
    public void sm()  //  valid 
    {    
        System.out.println("sub class");
    }
    public static void main(String a[])
       {    
        OREx s=new OREx();
        s.sm();      // sub class
       }
}

Demo2:
// super class ,Sub class methods throws unchecked exception 
package oops;

class Parentclass
{
    public void sm()throws Exception
    {
    System.out.println("super class");
    }
}  
public class OREx extends Parentclass
//Super ,Sub classes throws same exception noerror
public void sm()throws Exception  
    {    
        System.out.println("sub class");
    }
    public static void main(String a[])throws Exception
       {    
        OREx s=new OREx();
        s.sm();      // sub class
       }
}

Demo3:
// super class method no throws
// sub class method throws unchecked exception 
package oops;

class Parentclass
{
    public void sm()
    {
    System.out.println("super class");
    }
}  
public class OREx extends Parentclass{
    
    public void sm()throws Exception  // compile time error 
    //saying Exception Exception is not compatible with throws clause 
    {    
        System.out.println("sub class");
    }
    public static void main(String a[])throws Exception
       {    
        OREx s=new OREx();
        s.sm();     
       }
}