Strings

C#
string is an alias for String
String: UTF16

Java
UTF16

C++
wchar_t: UTF16 on Windows, UTF32 on Unix
wchar_t is not portable, better to use ICU instead.

stl::string
typedef basic_string < char > string;
typedef basic_string < wchar_t > wstring;
wstring string1 = L"obecně";

CString

ICU
UnicodeString: UTF16 internally. Note that the endianess of UTF-16 is platform dependent.
ICU does not use UCS-2. UCS-2 is a subset of UTF-16. UCS-2 does not support surrogates, and UTF-16 does support surrogates.

Note: most commonly, "Unicode" means UCS-2, but the difference between UCS-2 and UTF16 is not visible from the Java and C# standpoint

Windows TCHAR
#ifdef UNICODE
typedef wchar_t TCHAR;
#else
typedef char TCHAR;
#endif
TCHAR * toto = _T("obecně");

Note: in Java and C#, strings are immutable. String content cannot be changed after the object is created. See StringBuffer (Java) and StringBuilder (C#)