Unnecessary Temporary Instantiation

ID

kotlin.unnecessary_temp_instantiation

Severity

low

Remediation Complexity

medium

Remediation Risk

low

Remediation Effort

medium

Resource

Code Smell

Language

Kotlin

Tags

performance, redundant

Description

Reports throwaway boxed-wrapper constructions such as Integer("42") or Double("1.5"). Each one allocates a Java boxed wrapper from a string just to immediately unbox its primitive value. Kotlin offers direct literals (42, 1.5, 3L) and idiomatic string conversions ("42".toInt(), "1.5".toDouble()) that skip the allocation and read more clearly.

Rationale

// Bad
val a = Integer("42")    // FLAW — use 42 or "42".toInt()
val b = Long("3")        // FLAW
val c = Double("1.5")    // FLAW

// Good
val a = 42
val b = 3L
val c = 1.5

val d = "42".toInt()     // OK — explicit parse
val e = "1.5".toDouble() // OK — explicit parse

The boxed wrapper constructors are deprecated on the Java side as well — Integer(String) has been deprecated since JDK 9 in favour of Integer.parseInt(String) or Integer.valueOf(String). Kotlin’s literal and extension-based conversions are the idiomatic replacements.

Remediation

Replace Wrapper("literal") with the corresponding Kotlin literal when the argument is a constant, or with String.toInt() / String.toDouble() / etc. when the argument is a runtime string.

The rule fires only when the constructor has exactly one argument, so it does not interfere with rare multi-argument overloads.

References