checked exception issues in constructor

Demo 1:
package cons;
class P
{
  P() throws Exception // checked exception
  {
   }
}
public class C extends P{
    C()   //error (unhandled exception type exception)
    { 
        
    }
}

Demo 2:
package cons;
class P
{
  P()
  {
   }
}
public class C extends P{
    C()throws Exception   // no error
    { 
        
    }
}

Demo 3:
package cons;

import java.io.FileNotFoundException;
import java.io.IOException;

class P
{
    P()throws IOException 
    { 
    }
}
public class C extends P{
    C()throws FileNotFoundException // error
//  unhandled exception type IOexception
    { 
        
    }
}

Demo 4:
package cons;

import java.io.FileNotFoundException;
import java.io.IOException;

class P
{
    P()throws FileNotFoundException 
    { 
    }
}
public class C extends P{
    C()throws IOException //no error
    { 
        
    }
}
Note : no errors in case of unchecked exceptions