How can I get all the string in a java file??

How can I get all the string in a java file.

Example:
we have a java class file like this:
-test.java  -------------------------------------------------------------------------------------------------------------------
public class test{
      public static void correctString(String sourceFile, String desFile){
            String str1 = "Dang Nhon Hoa";
            String str2 = "Nguyen Quang Minh";
            String str3 = "Test1" + "test2" + "test3";

            System.out.print(str3 + str1 + str2 + "test");
      }
}
--------------------------------------------------------------------------------------------------------------------------
We have to write a method that read the java file above then return the expected String array content values like this:
            returnArrayValues = {"Dang Nhon Hoa", "Nguyen Quang Minh", "Test1", "test2", "test3", "test"};
This mean that all values that considered as String in java will be cacth to this list.
Thanks for your help.