Java Arrays compare() Method with Examples

The Arrays.compare() method in Java, available in the java.util.Arrays class, is used to compare two arrays lexicographically (dictionary order). It compares elements one by one to determine their ordering.

• Compares two arrays element by element in lexicographical order.
• Returns 0 if both arrays are equal.
• Returns a negative value if the first array is smaller, and a positive value if it is larger.

Example of Arrays.compare() method, where we compare two integer arrays with the same elements.

import java.util.Arrays;

public class ArrayCompare {
    public static void main(String[] args)
    {
        // Initialize two integer array with same elements
        int[] arr1 = { 1, 2, 3, 4 };
        int[] arr2 = { 1, 2, 3, 4 };
      
        // compare arr1 and arr2 using compare() method
        // and print the result
        System.out.println(
            "" + Arrays.compare(arr1, arr2));
    }
}

0

Explanation: The desired output is 0, because we are given two integer arrays with the same numbers and size.

Syntax of Arrays.compare() Method

Arrays.compare(arr1,arr2); // arr1 and arr2 are two arrays

Parameters: The compare() method accepts two arrays as parameters, with supported data types like String, Integer, Float, Double, Long, and others.

Return Type: The return type of this method is an integer.

• It returns positive value, if the first array is lexicographically greater.
• It returns negative value, if the first array is lexicographically lesser.
• It returns 0, if both arrays are equal.

Exceptions: NullPointerException: This exception is thrown, if an array is null when accessed.

Note: When comparing object arrays, if any element is null, it may throw a NullPointerException. To handle null values safely, use Arrays.compare() with a Comparator like Comparator.nullsFirst() or nullsLast().

What is Lexicographical Comparison

Lexicographical comparison means:

• Elements are compared from left to right
• The first mismatched element decides the result
• If all elements are equal, the array lengths are compared

This behavior is similar to how words are compared in a dictionary.

Examples of Arrays compare() Method with Different Data Types

Example 1: Compare Two Integer Arrays (Equal Arrays)

import java.util.Arrays;

public class CompareExample{
    public static void main(String[] args) 
    {
        
        //Initialized two integer array
        int[] arr1 ={6, 7, 8, 11, 18, 8, 2, 5};        
        int[] arr2 ={3, 5, 9, 13, 28, 6, 8, 9};
        
        //compare both integer array using compare method and finally print result       
        System.out.println(""+ Arrays.compare(arr1,arr2));

    }
}

1

Explanation: The result is positive because at the first mismatched index, the element in arr1 is greater than the corresponding element in arr2.

Example 2: Compare Two Float Arrays (Different Values)

import java.util.Arrays;

public class CompareExample{
  
    public static void main(String[] args) 
    {
        // Initialize two float array with element
        float[] arr1={5.12f, 8.3f, 9.17f, 2.5f, 8.8f, 5.17f, 4.2f, 7.37f};
        float[] arr2={7.12f, 9.3f, 6.17f, 7.5f, 5.8f, 7.17f, 3.2f, 6.37f};
      
        // compare two float array using compare method and finally print result
        System.out.println("" + Arrays.compare(arr1, arr2));
    }
}

-1

Explanation: The result is -1 in output because arr1 is lexicographically less than arr2.