How do I rebuild ANTLR v3?

Just run ant from the main directory where you see the build.xml file. Use the build target:

ant build

Or, for old people like Terence, you can do the following. Make sure the following two jars are in your CLASSPATH

antlr-3.0/lib/stringtemplate-3.0.jar
antlr-3.0/lib/antlr-2.7.7.jar

then jump into antlr-3.0/src directory and then type:

$ javac -d . org/antlr/Tool.java org/antlr/*/*.java org/antlr/*/*/*.java

Takes 9 seconds on my 1Ghz laptop or 4 seconds with jikes. Later I'll have a real build mechanism, though I must admit the one-liner appeals to me. I use Intellij so I never type anything actually to build.

Actually, this won't rebuild the grammars. If you touch the grammars, you need to convert all those Java:

cd antlr-3.0/src/org/antlr/tool
java antlr.Tool antlr.g
java antlr.Tool antlr.print.g
java antlr.Tool assign.types.g
java antlr.Tool define.g
java antlr.Tool buildnfa.g
cp ANTLRTokenTypes.txt ../codegen
pushd ../codegen; java antlr.Tool codegen.g; popd

That is for the v2-based grammars. There are actually two v3 grammars written in v3. Don't mess with them until I can rebuild all grammars in v3.