isEmpty()
The java string isEmpty() method checks if this string is empty. It returns true, if the length of the string is 0 otherwise false e.g.
System.out.println("".isEmpty()); // Prints - True
System.out.println(" ".isEmpty()); //Prints - False
Java 11 – isBlank()
The new instance method java.lang.String.isBlank() returns true if the string is empty or contains only white space,
where whitespace is defined as any codepoint that returns true when passed to Character#isWhitespace(int).
boolean blank = string.isBlank();
Before Java 11
boolean blank = string.trim().isEmpty();
After Java 11
boolean blank = string.isBlank();