Checking for string contents? string Length Vs Empty String

 

Which is more efficient for the compiler and the best practice for checking whether a string is blank?

  • Checking whether the length of the string == 0
  • Checking whether the string is empty (strVar == "")

    • Also, does the answer depend on language?

    Yes, it depends on language, since string storage differs between languages.

  • Pascal-type strings: Length = 0 .
  • C-style strings: [0] == 0 .
  • .NET: .IsNullOrEmpty .

    • Etc.

    In languages that use C-style (null-terminated) strings, comparing to "" will be faster. That's an O(1) operation, while taking the length of a C-style string is O(n).

    In languages that store length as part of the string object (C#, Java, ...) checking the length is also O(1). In this case, directly checking the length is faster, because it avoids the overhead of constructing the new empty string.

    In .Net: 

    string.IsNullOrEmpty( nystr );

    strings can be null, so .Length sometimes throws a NullReferenceException

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