While hashCode and toString are available on arrays, they are largely useless. hashCode returns the array’s "identity hash code", and toString returns nearly the same value. Neither method’s output actually reflects the array’s contents. Furthermore, contentHashCode() and contentToString() are also useless on arrays of array.

Instead, you should use:

• On array of objects or arrays: contentDeepHashCode() and contentDeepToString()
• On array of primitives: contentHashCode() and contentToString()

Noncompliant Code Example

fun main() {
    val primitiveArray = intArrayOf(1, 2, 3)
    val objectArray = arrayOf("A", "B", "C")
    val arrayOfArray = arrayOf(arrayOf("A", "B"), arrayOf("C", "D"))

    println(primitiveArray.toString())       // Noncompliant, output: [I@2acf57e3
    println(primitiveArray.hashCode())       // Noncompliant, output: 718231523
    println(objectArray.toString())          // Noncompliant, output: [Ljava.lang.String;@506e6d5e
    println(objectArray.hashCode())          // Noncompliant, output: 1349414238
    println(arrayOfArray.toString())         // Noncompliant, output: [[Ljava.lang.String;@96532d6
    println(arrayOfArray.contentToString())  // Noncompliant, output: [[Ljava.lang.String;@3796751b, [Ljava.lang.String;@67b64c45]
    println(arrayOfArray.hashCode())         // Noncompliant, output: 157627094
    println(arrayOfArray.contentHashCode())  // Noncompliant, output: 586055243
}

Compliant Solution

fun main() {
    val primitiveArray = intArrayOf(1, 2, 3)
    val objectArray = arrayOf("A", "B", "C")
    val arrayOfArray = arrayOf(arrayOf("A", "B"), arrayOf("C", "D"))

    println(primitiveArray.contentToString())   // Compliant, output: [1, 2, 3]
    println(primitiveArray.contentHashCode())   // Compliant, output: 30817
    println(objectArray.contentDeepToString())  // Compliant, output: [A, B, C]
    println(objectArray.contentDeepHashCode())  // Compliant, output: 94369
    println(arrayOfArray.contentDeepToString()) // Compliant, output: [[A, B], [C, D]]
    println(arrayOfArray.contentDeepHashCode()) // Compliant, output: 98369
}