#if in java, as in c preprocessors

Question

Possible duplicate:
How to mark Java code so that it does not compile

In c , we can prevent compilation of block code as follows:

#if 0 //code here #endif 

So even if a code block with an error is prone to compiling code, I want the same thing in Java so that I can skip the part of the code that will not compile because some library is missing.

Can anybody help me?

Answer 1

You must comment on the code , you cannot use the preprocessor directive in java.

Answer 2

There is no preprocessor in Java. Depending on your build system, you can use a third-party preprocessor (you can find many of them by searching for “Java preprocessor”). Some examples

• Java preprocessor
• Java preprocessor comment
• javapp
• prebop

Depending on the area you want to comment out, you can use block comments and sometimes something like

 if (false) { . . . } 

If all else fails, just comment out each line using // . Most IDEs have a way to do this (and undo it) efficiently.

PS If you can use block comments (this is not always possible, since block comments cannot be embedded in Java), there is a good trick to minimize the amount of work that needs to be done to disable and leave the commented part out. Start your block comment on a separate line, but end it with another isolated line starting with a line comment, for example:

 /* <block of code ignored as comment> //*/ 

Then, if you want to re-enable the commented section, just add a second / at the beginning of the block:

 //* <block of code now active> //*/ 

To disable the code again, simply delete the first / .

Answer 3

I assume that the compiler will block code inside blocks with forced / final flags? Here is how you can leave the code in your project that is not sent to the final apk.

 public final static boolean DEBUG = false; if(DEBUG) { //add messy error prone code here //compiler will strip this out as unreachable when false } 

Read here:

http://docs.oracle.com/javase/specs/jls/se7/html/jls-14.html#jls-14.21

Answer 4

In Java, there is no preprocessor for C lines.

Since, according to the tags, you are using Eclipse, you can simply mark the entire block of code that you want to comment on, then use CTRL - / .

You can also use the same key sequence to uncomment an already commented out block.

Answer 5

One of the methods I used is to use m4 as a preprocessor for java files. You write your code in classname.java.m4 and use a Makefile or other build system rule to run m4:

 %: %.m4 @echo "/* automatically generated from $< -- don not edit*/" > $@ m4 $< >> $@ 

Answer 6

java Do not provide pre-processor facility.

By the way, you can use the comment as below:

you are using Eclipse, you can simply mark the entire block of code you want to comment on, then use CTRL + SHIFT + C for comments and uncommentation of the block of code.