Should I use string.isEmpty() or "".equals(string)?

Decoding the methods

string.isEmpty() is Java's quintessential measure for speed. It peeks at the string's count variable, which details the character count, comparing the count with zero.

"".equals(string), on the other hand, takes a tour through three checks - same object reference, matching types, and identical characters. Resultantly, isEmpty() clinches the efficiency medal by being a three-time champ over "".equals(string).

The right string for the right time

Ideally, use:

• string.isEmpty():

  • When you've verified that string is not null.
  • In a Java 1.6 or later environment.
  • For optimal performance when validating an empty string.

• "".equals(string):

  • If the string could possibly be null.
  • For older Java (1.5 or older) code compatibility.
  • When null-safety trumps performance.

Apache Commons StringUtils: the jack of all checks

In between our two contenders, we have the sturdy StringUtils.isEmpty(). It checks for null and empty strings in one go:

if (StringUtils.isEmpty(string)) {
    // Handles null and empty strings in one fell swoop!
}


Apache's StringUtils further impresses with the isBlank() method, considering whitespace-only strings. This library is a win-win for code readability and bug prevention.

Avoiding the booby traps

Prevent the dreaded NullPointerException:

• By performing a null check before applying methods.
• Utilizing Java Optional type or annotations like @Nullable and @NotNull.
• Using try-catch blocks to ward off exceptions with null or empty strings.

Good practices and their benefits

Achieving a balance with performance and readability is vital. With isEmpty() and "".equals(string), consider:

• Consistency: Stick with your string check style.
• Documentation: Comment on why a particular check is chosen.
• Clarity in intent: Make the code speak for itself.