Java Program to Check if a String is Empty or Null

Example 1: Check if String is Empty or Null

Output

str1 is NULL
str2 is EMPTY
str3 is neither NULL nor EMPTY

In the above program, we have created

• a null string str1
• an empty string str2
• a string with white spaces str3
• method isNullEmpty() to check if a string is null or empty

Here, str3 only consists of empty spaces. However, the program doesn't consider it an empty string.

This is because white spaces are treated as characters in Java and the string with white spaces is a regular string.

Now, if we want the program to consider strings with white spaces as empty strings, we can use the trim() method. The method removes all the white spaces present in a string.

Example 2: Check if String with spaces is Empty or Null

Output

str is EMPTY

In the above example, notice the condition to check empty string

else if (str.trim().isEmpty())

Here, we have used the trim() method before isEmpty(). This will

1. remove all the white spaces present inside the string
2. check if the string is empty

Hence, we get str is EMPTY as output.