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In object-oriented programming, "immutable interface" is a pattern for designing an immutable object. [1] The immutable interface pattern involves defining a type which does not provide any methods which mutate state. Objects which are referenced by that type are not seen to have any mutable state, and appear immutable.
In Java [5]: 84 these are StringBuffer and StringBuilder (mutable versions of Java String) and in .NET this is StringBuilder (mutable version of .Net String). Python 3 has a mutable string (bytes) variant, named bytearray. [6] Additionally, all of the primitive wrapper classes in Java are immutable.
Primitive wrapper classes are not the same thing as primitive types. Whereas variables, for example, can be declared in Java as data types double, short, int, etc., the primitive wrapper classes create instantiated objects and methods that inherit but hide the primitive data types, not like variables that are assigned the data type values.
One might desire to have a LinkedList of int, but this is not directly possible. Instead Java defines primitive wrapper classes corresponding to each primitive type: Integer and int, Character and char, Float and float, etc. One can then define a LinkedList using the boxed type Integer and insert int values into the list by boxing them as ...
Final variables can be used to construct trees of immutable objects. Once constructed, these objects are guaranteed not to change anymore. To achieve this, an immutable class must only have final fields, and these final fields may only have immutable types themselves. Java's primitive types are immutable, as are strings and several other classes.
Integer addition, for example, can be performed as a single machine instruction, and some offer specific instructions to process sequences of characters with a single instruction. [7] But the choice of primitive data type may affect performance, for example it is faster using SIMD operations and data types to operate on an array of floats.
In a number of object-oriented languages, there is the concept of an immutable object, which is particularly used for basic types like strings; notable examples include Java, JavaScript, Python, and C#. These languages vary in whether user-defined types can be marked as immutable, and may allow particular fields (attributes) of an object or ...
The data type should preferably be immutable if possible. It is common for implementations to handle equality testing, serialization and model binding. The strongly typed identifier commonly wraps the data type used as the primary key in the database, such as a string, an integer or universally unique identifier (UUID).