Checking if a String is Not Null and Not Empty

To determine if a string is not null and not empty, Java provides various methods.

Option 1: isEmpty()

For Java versions 1.6 and later, the isEmpty() method provides a concise way to check for emptiness:

if (str != null && !str.isEmpty())

Option 2: str.length() == 0

For Java versions prior to 1.6, str.length() == 0 can be used:

if (str != null && str.length() == 0)

Option 3: trim().isEmpty()

To ignore leading and trailing whitespace, use trim().isEmpty():

if (str != null && !str.trim().isEmpty())

Option 4: isBlank()

Java 11 introduced the isBlank() method, which combines the functionality of isEmpty() and trim():

if (str != null && !str.isBlank())

Handy Function

To simplify the task, consider wrapping the logic in a function:

public static boolean empty(String s) {
  return s == null || s.trim().isEmpty();
}

// Usage
if (!empty(str))