What is Validate.notNull in Java?

notNull() is a staticthe methods in Java that can be called without creating an object of the class. method of the Validate class that is used to check whether the passed object is null or not.

  • If the passed object is null, then the method raises an exception with a formatted message.
  • If the passed object is not null, then the method returns the input as it is.

How to import Validate

The definition of Validate can be found in the Apache Commons Lang package, which we can add to the Maven project by adding the following dependency to the pom.xml file:

<dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>3.12.0</version>
</dependency>

For other versions of the commons-lang package, refer to the Maven Repository.

You can import the Validate class as follows.

import org.apache.commons.lang3.Validate;

Syntax

public static <T> T notNull(T object, String message, Object... values)

Parameters

  • object: The object to check if it is null.
  • message: The exception message if the object is invalid.
  • values: The optional values for the formatted exception message.

Return value

This method throws a NullPointerException if the object is null. Otherwise, it doesn’t return anything.

Code

import org.apache.commons.lang3.Validate;
public class Main{
    public static void main(String[] args){
        String stringToValidate = "hello";
        System.out.printf("Validate.notNull(%s) = %s", stringToValidate, Validate.notNull(stringToValidate));
        System.out.println();
        String exceptionMessageFormat = "Argument should not be null";
        stringToValidate = null;
        System.out.printf("Validate.notNull(%s) = %s", stringToValidate, Validate.notNull(stringToValidate, exceptionMessageFormat));
        System.out.println();
    }
}

Output

The output of the code will be as follows:

Validate.notNull(hello) = hello

Exception in thread "main" java.lang.NullPointerException: Argument should not be null
	at java.base/java.util.Objects.requireNonNull(Objects.java:347)
	at org.apache.commons.lang3.Validate.notNull(Validate.java:224)
	at Main.main(Main.java:12)

Explanation

Example 1

  • stringToValidate = "hello"

The method returns the input value hello as it is not a null value.

Example 2

  • stringToValidate = null
  • exceptionMessageFormat = "Argument should not be null"

The method throws a NullPointerException as the input value is null.

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