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However, Java initially left open the possibility of implementing const, noticeable in that const is a reserved word, though it is not actually used as a keyword. Instead, Java has the object-oriented keyword final , which is used to qualify attributes (and thence also for local variables) as constant, but not to qualify types.
Besides the static constants described above, many procedural languages such as Ada and C++ extend the concept of constantness toward global variables that are created at initialization time, local variables that are automatically created at runtime on the stack or in registers, to dynamically allocated memory that is accessed by pointer, and to parameter lists in function headers.
because the argument to f must be a variable integer, but i is a constant integer. This matching is a form of program correctness, and is known as const-correctness.This allows a form of programming by contract, where functions specify as part of their type signature whether they modify their arguments or not, and whether their return value is modifiable or not.
A much more human-friendly rendition of machine language, named assembly language, uses mnemonic codes to refer to machine code instructions, rather than using the instructions' numeric values directly, and uses symbolic names to refer to storage locations and sometimes registers. [3]
In imperative languages, the same behavior is exhibited by (named) constants (symbolic constants), which are typically contrasted with (normal) variables. Depending on the type system of a programming language, variables may only be able to store a specified data type (e.g. integer or string). Alternatively, a datatype may be associated only ...
Many files have such constants that identify the contained data. Detecting such constants in files is a simple and effective way of distinguishing between many file formats and can yield further run-time information. Examples. Compiled Java class files and Mach-O binaries start with hex CAFEBABE.
push a constant #index from a constant pool (String, int, float, Class, java.lang.invoke.MethodType, java.lang.invoke.MethodHandle, or a dynamically-computed constant) onto the stack (wide index is constructed as indexbyte1 << 8 | indexbyte2) ldc2_w 14 0001 0100 2: indexbyte1, indexbyte2 → value
The Java type system, however, treats enumerations as a type separate from integers, and intermixing of enum and integer values is not allowed. In fact, an enum type in Java is actually a special compiler-generated class rather than an arithmetic type, and enum values behave as global pre-generated instances of that class. Enum types can have ...