What is conditional compilation in Java?
The conditional compilation practice is used to optionally remove chunks of code from the compiled version of a class. It uses the fact that compilers will ignore any unreachable branches of code. To implement conditional compilation, define a static final boolean value as a non-private member of some class.
Does Java have Ifdef?
Java does not include any kind of preprocessor like the C cpp preprocessor. It may seem hard to imagine programming without #define, #include, and #ifdef, but in fact, Java really does not require these constructs.
What is meant by conditional compilation?
Conditional compilation provides a way of including or omitting selected lines of source code depending on the values of literals specified by the DEFINE directive. In this way, you can create multiple variants of the same program without the need to maintain separate source streams.
Why is conditional compilation used?
In computer programming, conditional compilation is compilation implementing methods which allow the compiler to produce differences in the executable program produced and controlled by parameters that are provided during compilation.
What is true about conditional compilation?
Does Java have a preprocessor?
Java implementation does not have a preprocessor.
Does Java have preprocessor?
Are there macros in Java?
Java itself doesn’t support macros. On the other hand, you could pipe the source code through the C preprocessor (CPP for short) just like the C/C++ compile chain does.
How do you use conditional compilation?
Conditional compilation directives can be nested….The directives are:
- The #if and #elif directives, which conditionally include or suppress portions of source code, depending on the result of a constant expression.
- The #ifdef directive, which conditionally includes source text if a macro name is defined.
What statement are used for conditional compilation?
The $ELSE statement is used in conjunction with the $IF statement to control conditional compilation. The $END statement is used in conjunction with the $IF statement to control conditional compilation. A $IF statement provides the means whereby selected parts of the source text are not included in the compilation.
What statements are used for conditional compilation?
What is the difference between #ifdef and #ifndef?
The defined( identifier ) constant expression used with the #if directive is preferred. The #ifndef directive checks for the opposite of the condition checked by #ifdef . If the identifier hasn’t been defined, or if its definition has been removed with #undef , the condition is true (nonzero).
Is there Typedef in Java?
There is no typedef mechanism in Java. You should definitely consider having a subclass for that purpose.
How do you #define in Java?
Java doesn’t have a general purpose define preprocessor directive. private static final int PROTEINS = 100; Such declarations would be inlined by the compilers (if the value is a compile-time constant).
Can Ifdef be nested?
#ifdef directives can be nested, however, all directives in a given logical level must exist in a single file. The following sample code showing use of the #ifdef directive chain with nested #ifdefs. The expression #ifndef Name evaluates to true in Name has not been #defined.
How do you use Ifndef?
#ifndef is often used to make header files idempotent by defining a token once the file has been included and checking that the token was not set at the top of that file. Identifiers starting with an underscore are reserved; you shouldn’t define them yourself. Use something like #ifndef H_HEADER_NAME .
What is the difference between #ifdef and #if defined?
The difference between the two is that #ifdef can only use a single condition, while #if defined(NAME) can do compound conditionals.