What is ArrayUtils.lastIndexOf in Java?
lastIndexOf is a static method of the ArrayUtils class that finds the index of the last occurrence of an element in the array.
The method returns -1 if the element is not found in the array or if the passed array is null.
Syntax
public static int lastIndexOf(final int[] array, final int valueToFind)
Parameters
-
final int[] array: array of elements. -
final int valueToFindthe element to find.
Return value
The method returns the index of the last occurrence of the element, -1, if the element is not found in the array.
Add the Apache Commons-Lang package
ArrayUtils is defined in the Apache Commons Lang package. Apache Commons Lang can be added 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.
How to import ArrayUtils
You can import the ArrayUtils class as follows.
import org.apache.commons.lang3.ArrayUtils;
Code
Example 1
array = [1,2,3,4,5,2,3,2,2,4]element = 2
The lastIndexOf function returns 8, i.e., the index of the last occurrence of the element 2.
Example 2
array = [1,2,3,4,5]offset = -2
The lastIndexOf function returns -1, as the element is not found in the array.
import org.apache.commons.lang3.ArrayUtils;
public class Main {
public static void main(String[] args) {
int[] array = {1,2,3,4,5,2,3,2,2,4};
int element = 2;
int index = ArrayUtils.lastIndexOf(array, element);
System.out.println("The index of the last occurrence of " + element + " is " + index);
element = -2;
index = ArrayUtils.lastIndexOf(array, element);
System.out.println("The index of the last occurrence of " + element + " is " + index);
}
}Output
The index of the last occurrence of 2 is 8
The index of the last occurrence of -2 is -1
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