Question

I maintain a Java Swing application.

For backwards compatibility with java 5 (for Apple machines), we maintain two codebases, 1 using features from Java 6, another without those features.

The code is largely the same, except for 3-4 classes that uses Java 6 features.

I wish to just maintain 1 codebase. Is there a way during compilation, to get the Java 5 compiler to ‘ignore’ some parts of my code?

I do not wish to simply comment/uncomment parts of my code, depending on the version of my java compiler.

Answer 1

Assuming that the classes have similar functionality with 1.5 vs. 6.0 differences in implementation you could merge them into one class. Then, without editing the source to comment/uncomment, you can rely on the optimization that the compiler always do. If an if expression is always false, the code in the if statement will not be included in the compilation.

You can make a static variable in one of your classes to determine which version you want to run:

public static final boolean COMPILED_IN_JAVA_6 = false; 

And then have the affected classes check that static variable and put the different sections of code in a simple if statement

if (VersionUtil.COMPILED_IN_JAVA_6) {   // Java 6 stuff goes here } else {   // Java 1.5 stuff goes here } 

Then when you want to compile the other version you just have to change that one variable and recompile. It might make the java file larger but it will consolidate your code and eliminate any code duplication that you have. Your editor may complain about unreachable code or whatever but the compiler should blissfully ignore it.