import java.io.IOException;

public class A  {
     public void test() throws IOException{
        System.out.println("test in A");
    }
}

import java.io.IOException;

  public   class B extends A {
      @Override
      public  void test() throws Exception{
          System.out.println("test in B");
      }
 }

public void test() throws IOException{//<--header of A
    System.out.println("test in B");//<--body of B
    //here i can throw wide Exception from IOException
    //because here is body of test in B.test method in B can throws Exception so compiler doesn't approve this version of code
 }

A a = new B(); //when compiler converts this line into bytecode
//does it loads of method headers of A and method body's of B
a.test()

A a = new B();
try {
  a.test();
} catch (IOExceoption e) {
   //do some specific handle for IOExceoption
}

public class A  {
     public void test() throws Exception {
        System.out.println("test in A");
    }
}
  public   class B extends A {
      @Override
      public  void test() throws IOException{
          System.out.println("test in B");
      }
 }

A a = new B();
try {
  a.test();
} catch (Exception e) {
   //handle
}