Java String isEmpty() method
Syntax and Examples

Introduction

Sometimes you need to know if a string contains any characters or not. The isEmpty() method in Java provides a simple and direct way to determine whether a String object is empty.

Syntax

public boolean isEmpty()

Parameters

Parameter	Description
None	This method doesn't accept any parameters.

Return Value

The isEmpty() method returns a boolean value:

• true: If the string has length 0 (it's empty).
• false: If the string has any characters.

Examples

Example 1: Checking an Empty String

This example demonstrates how to use isEmpty() with a truly empty string.

public class Main {
    public static void main(String[] args) {
        String str = ""; // An empty string
        boolean isEmpty = str.isEmpty();
        System.out.println("Is the string empty? " + isEmpty);
    }
}

Is the string empty? true

Here, we create a String variable str and initialize it with an empty string (""). We then call isEmpty() on this string. Since the string is empty, isEmpty() returns true.

Example 2: Checking a Non-Empty String

This example illustrates how isEmpty() behaves with a string that contains characters.

public class Main {
    public static void main(String[] args) {
        String str = "Hello"; // A non-empty string
        boolean isEmpty = str.isEmpty();
        System.out.println("Is the string empty? " + isEmpty);
    }
}

Is the string empty? false

In this case, str is initialized with the value “Hello”. Since the string has characters, isEmpty() returns false.

Example 3: Checking a String Containing Only Whitespace

This example demonstrates that whitespace-only strings are *not* considered empty by isEmpty(). They have length greater than zero.

public class Main {
    public static void main(String[] args) {
        String str = "   "; // A string containing only whitespace
        boolean isEmpty = str.isEmpty();
        System.out.println("Is the string empty? " + isEmpty);
    }
}

Is the string empty? false

Even though str contains only spaces, it's not considered an empty string because its length is greater than zero. Therefore, isEmpty() returns false.

Example 4: Using isEmpty() for Validation

This example shows how you might use isEmpty() to validate user input before processing it.

public class Main {
    public static void main(String[] args) {
        String userInput = null;
        if (userInput == null || userInput.isEmpty()) {
            System.out.println("User input is empty or null.  Please provide some data.");
        } else {
            System.out.println("Processing user input: " + userInput);
        }
    }
}

User input is empty or null.  Please provide some data.

Here, we check if the userInput variable is either null (meaning it hasn't been assigned a value) or empty using isEmpty(). If either condition is true, we display an error message to the user. Otherwise, we proceed with processing the input.