Write a Python program to swap cases of a given string.

def swap_case_string(str1):
   result_str = ""   
   for item in str1:
       if item.isupper():
           result_str += item.lower()
       else:
           result_str += item.upper()           
   return result_str
print(swap_case_string("Python Exercises"))
print(swap_case_string("Java"))
print(swap_case_string("NumPy"))