CODEWITHSUNDEEP
javacompilationcross-platform
Primm
Primm

Reputation: 1387

How do I compile a .java with support for older versions of Java?

I want to compile my .java's (several) into one .jar that are compatible with at least Java 1.6 and newer, preferably Java 1.5 and newer versions of Java. (I have Java 1.7.0_5)

Upvotes: 48

Views: 83222

Answers (6)

INDRAJITH EKANAYAKE
INDRAJITH EKANAYAKE

Reputation: 4294

The following command will compile all your java classes with java version 1.8 because by default your code compiled by the latest version which you have.

javac -source 1.8 -target 1.8  *.java

Upvotes: 0

Joe Darcy
Joe Darcy

Reputation: 371

As of JDK 9, javac support a new option for cross-compiling

javac --release N ...

which is equivalent to

javac -source N -target N –bootclasspath rtN.jar

Upvotes: 32

gtiwari333
gtiwari333

Reputation: 25174

Yes, you can set the version of compiler at compile time. And compile your java code into old versions of java.

From Oracle article : http://docs.oracle.com/javase/1.5.0/docs/tooldocs/windows/javac.html

Cross-Compilation Example

Here we use javac to compile code that will run on a 1.4 VM.

% javac -target 1.4 -bootclasspath jdk1.4.2/lib/classes.zip \
             -extdirs "" OldCode.java

You might also need following parameter to set denote the version of your code.

-source release

-Specifies the version of source code accepted.

Upvotes: 30

eckes
eckes

Reputation: 10433

You can specify the target version of the compiler lower than the build java version (all answers basically said that) but you should not: it is quite messy as it only works if you also supply the class libraries for the actual target version. If you do that you are much better off with simply using this old Java version to compile. Much cleaner and less stuff to setup. For Java 9 the options are a bit nicer but you still need an old JDK lying around for the rt.jar.

What you can do is in your ide and dedvelopment cycle use the -target/-bootclasspath trick to get faster compiler and better warnings, but IT and release builds then should be done with the target version.

Upvotes: 1

tofarr
tofarr

Reputation: 7851

You can use the newest version of the JDK and set the source level to 1.5 - as long as you don't use classes / methods that were introduced after 1.5 you should be ok for all versions of the JVM 1.5 and above:

-source 1.5

Upvotes: 0

cha0site
cha0site

Reputation: 10737

You can use javac -target 1.5 <source files>.

If you're using a build system, Eclipse or some other IDE to build jars, please specify which one.

Upvotes: 3

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