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
}
