Boxed primitive
A boxed primitive is a reference or object type that represents a corresponding primitive value and provides object semantics, including possible nullability.
100 Java Mistakes and How to Avoid Them
A boxed primitive type is a reference type that wraps a Java primitive value, such as Integer wrapping int, and can represent null.
- How it is used
- Prevents null-unboxing and comparison mistakes when Java code uses primitive wrapper types.
- How deep it goes
- Explains conditional-expression type conversion and autounboxing consequences, while recommending if statements instead of memorizing all rules.
- Examples
- Uses Double value-or-zero conditionals, nested Integer mapping, a three-outcome confirmation, and cached Integer comparisons.
- What you can do after
- Diagnose/debug null-unboxing and unreliable wrapper equality, then replace fragile expressions with primitives, if statements, enums, or equals().
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Kotlin in Action, 2E
A wrapper type is a Java reference type that represents a value of a corresponding primitive type, such as Integer for int.
- How it is used
- Explains JVM representation choices behind Kotlin numeric types, especially during Java interoperability, null handling, and generic collection use.
- How deep it goes
- Traces boxing from Java’s primitive-reference distinction through Kotlin syntax, nullable types, generic limitations, and collection consequences.
- Examples
- Uses Int declarations, List<Int>, nullable Person.age, and comparisons involving missing ages.
- What you can do after
- Evaluate when Kotlin values become Java wrappers and choose nullable types, collections, arrays, or specialized storage accordingly.
Related concepts
- nullable typeused by · A nullable type is a type whose values may be either a value of the underlying type or an explicit representation of absence, such as null.
- float64includes · Float64 is a 64-bit floating-point numeric type, commonly represented using the IEEE 754 binary64 format.
- primitive data typealternative to · A primitive data type is a fundamental, language-provided type for representing a basic value, rather than a composite of multiple values.
- specialized primitive collectionalternative to · A specialized primitive collection is a collection implementation that stores primitive values directly and provides operations accepting those values without boxing.
- implicit conversionuses · Implicit conversion is an automatic change of a value from one type to another according to language rules, without an explicit conversion operation in the source code.
- conditional logicproduced by · Conditional logic is a programming technique that selects execution paths, actions, or result values according to evaluated conditions.
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