Map Not-Null Assertion

ID

kotlin.map_not_null_assertion

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Kotlin

Tags

collections, null-safety

Description

Reports index access expressions immediately followed by !!.

map[key] returns null when the key is absent, and map[key]!! then throws a NullPointerException — a less informative exception than the NoSuchElementException that map.getValue(key) would throw.

Rationale

val name = users[id]!!        // FLAW — NPE if id not in map

val name = users.getValue(id)       // OK — NoSuchElementException, descriptive
val name = users[id] ?: "unknown"   // OK — null-safe fallback
val name = users[id]?.uppercase()   // OK — safe call

Remediation

  • Use map.getValue(key) when the key must be present (throws NoSuchElementException).

  • Use map[key] ?: default when a fallback is acceptable.

  • Use map[key]?.let { …​ } to act only when the key is present.

References