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The most significant are: compile-time (statically valued) constants, run-time (dynamically valued) constants, immutable objects, and constant types . Typical examples of compile-time constants include mathematical constants, values from standards (here maximum transmission unit ), or internal configuration values (here characters per line ...
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.
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.
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 ...
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.
The predominant paradigm for concurrency in mainstream languages such as Java is shared memory concurrency. Concurrent languages that make use of message passing have generally been inspired by process calculi such as communicating sequential processes (CSP) or the π-calculus .
An exception is when a processor is designed to use a particular bytecode directly as its machine code, such as is the case with Java processors. Machine code and assembly code are sometimes called native code when referring to platform-dependent parts of language features or libraries.