How to Check if String is Null in Java - Simple Guide

In Java, you check if a string is null by using the condition string == null. This compares the string variable to null to see if it has no value assigned.

Syntax

Use the equality operator == to check if a string is null. The syntax is:

• stringVariable == null returns true if the string has no value.
• stringVariable != null returns true if the string has some value.

java

if (stringVariable == null) {
    // string is null
} else {
    // string is not null
}

Example

This example shows how to check if a string is null and print a message accordingly.

java

public class NullCheckExample {
    public static void main(String[] args) {
        String text = null;

        if (text == null) {
            System.out.println("The string is null.");
        } else {
            System.out.println("The string is not null.");
        }

        text = "Hello";

        if (text == null) {
            System.out.println("The string is null.");
        } else {
            System.out.println("The string is not null.");
        }
    }
}

Output

The string is null.
The string is not null.

Common Pitfalls

A common mistake is to use string.equals(null) to check for null. This causes a NullPointerException if the string is actually null. Always use == null to check for null before calling any methods on the string.

Wrong way:

if (string.equals(null)) {
    // This throws NullPointerException if string is null
}

Right way:

if (string == null) {
    // Safe null check
}

Quick Reference

Check	Syntax	Meaning
Is null	string == null	String has no value assigned
Is not null	string != null	String has some value

Key Takeaways

Use 'string == null' to safely check if a string is null in Java.

Never use 'string.equals(null)' as it throws an error if string is null.

Check for null before calling any methods on a string to avoid exceptions.

Use 'string != null' to confirm a string has a value before using it.