Junit test cases for a nested do while loop

Here is the skeletal for the code:

    flag1=True
    flag2=True
    do {

        try {

            if (){
                throw new IllegalArgumentException();
            }
            .
            .
            .
           do {

                if () {


                } 
               else {

                }
                .
                . 
                .
                if () {
                }

            } while (flag2);

            flag1 = false;

        } catch (RuntimeException ex) {

            retry = true;
        } catch (Exception ex) {

            flag1 = true;


        } catch (Error ex) {

            flag1= true;
        }
        }

    } while (flag1);
}

I am using junit4 for testing. I need to cover all the try catch blocks for testing as well. I wrote a test case satisfying the first if condition and hence throwing illegal argument exception, but after throwing the exception the code moves to the do loop with flag1 always staying true.