Antlr3 Code Too Big

Antlr3 can generate very large java files for complex grammars.
Javac can have a problem compiling them due to the size limit of static initializers in a class file.

An error like the following

: code too large
> > [12:56:12] public static final String[] tokenNames = new String[] {
> > [12:56:12] ^
> > [12:56:12] 1 error

My solution was to post process the generated Java files.
Moving a large section of static final initializers to a seperate interface(s).
Then reference (implement) the interface in the original Java file.

package oracle.dtools.ant.antlr3;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

import org.apache.tools.ant.Task;

public class Antlr3PostProcess extends Task {
    private File oldTarget = null;
    private String pkg = null;
    
    private File newTarget= null;
    private File currentInterface = null;
    private int interfaceIndex = 0;
    private int lineIndex = 0;
    private final int MAXLINEINDEX = 1000;
    private String name = null;
    
    public Antlr3PostProcess(){
    }

    public String getPkg() {
        return pkg;
    }

    public void setPkg(String pkg) {
        this.pkg = pkg;
    }
    
    public File getTarget() {
        return oldTarget;
    }
    
    public void setOldTarget(File oldTarget) {
        name = oldTarget.getName().substring(0,oldTarget.getName().indexOf('.'));
        this.oldTarget = oldTarget;
        newTarget = new File(oldTarget.getParentFile(),name+"_TMPANTLR3POST.java");
    }

    public void execute() {
        try{
         boolean createFile =  newTarget.createNewFile();
        moveBitSetConstantsToInterface();
        //delete the old target and rename the new target
        oldTarget.delete();
        newTarget.renameTo(oldTarget);
        } catch (Exception e){
           
        }
    }

    private void moveBitSetConstantsToInterface() throws IOException {
      //open the target file
        BufferedReader reader = new BufferedReader(new FileReader(oldTarget));
        BufferedWriter writerInterface = getNewInterfaceWriter();
        BufferedWriter writerNewTarget = new BufferedWriter(new FileWriter(newTarget));

        //... Loop as long as there are input lines.
        String line = null;
        while ((line=reader.readLine()) != null) {        
            if(lineIndex > MAXLINEINDEX) {
                lineIndex =0;
                closeInterface(writerInterface)  ;
                writerInterface  = getNewInterfaceWriter();
            }
            if(line.startsWith("    public static final BitSet FOLLOW_")){
                lineIndex++;
                writerInterface.write(line); 
                writerInterface.newLine();   // Write system dependent end of line.
            } else if (line.startsWith("public class "+name+" extends Parser")) {
                writerNewTarget.write("public class "+name+" extends Parser implements "+getInterfaceName() +" {"); 
                writerNewTarget.newLine();   // Write system dependent end of line.
            }
            else {
                writerNewTarget.write(line); 
                writerNewTarget.newLine();   // Write system dependent end of line.
            }
            
        }
        closeInterface(writerInterface);
        //... Close reader and writer.
        reader.close();  // Close to unlock.
        //writerInterface.close();  // Close to unlock and flush to disk.
        writerNewTarget.close();  // Close to unlock and flush to disk.
        createInterfaceGroup();
    }


    private void createInterfaceGroup() throws IOException {
        currentInterface = new File(oldTarget.getParentFile(),getInterfaceName()+".java");
        boolean createFile =currentInterface.createNewFile(); 
        BufferedWriter writerInterface =  new BufferedWriter(new FileWriter(currentInterface));
        writerInterface.write("package "+pkg+";");
        writerInterface.newLine();
        writerInterface.write("import org.antlr.runtime.BitSet;");
        writerInterface.newLine();
        writerInterface.write("public interface "+getInterfaceName()+" extends ");
        writerInterface.write(getInterfaceName()+"1");
        for(int i=2;i<=interfaceIndex;i++){
            writerInterface.write(","+getInterfaceName()+i);
        }
        writerInterface.write(" {");
        writerInterface.newLine(); 
        writerInterface.write("}");
        writerInterface.close();
        
    }

    private void closeInterface(BufferedWriter writerInterface) throws IOException {
        writerInterface.newLine();
        writerInterface.write("}");  
        writerInterface.close();
    }

    private BufferedWriter getNewInterfaceWriter() throws IOException {
        BufferedWriter writerInterface =  new BufferedWriter(new FileWriter(getNextInterfaceFile()));
        createInterfaceHeading(writerInterface,currentInterface.getName().substring(0,currentInterface.getName().indexOf('.')),pkg);
        return writerInterface;
     
    }

    private void createInterfaceHeading(BufferedWriter writerInterface,String interfaceName, String interfacePkg) throws IOException {
        writerInterface.write("package "+interfacePkg+";");
        writerInterface.newLine();
        writerInterface.write("import org.antlr.runtime.BitSet;");
        writerInterface.newLine();
        writerInterface.write("public interface "+interfaceName+" {");
        writerInterface.newLine();
    }

    private File getNextInterfaceFile() throws IOException {
        interfaceIndex++;
        currentInterface = new File(oldTarget.getParentFile(),getInterfaceName()+interfaceIndex+".java");
        boolean createFile =currentInterface.createNewFile(); 
        return currentInterface;
    }

    private String getInterfaceName() {
        return name+"BitSet";
    }
}

Define the Ant Task

<taskdef name="Antlr3PostProcess" classname="oracle.dtools.ant.antlr3.Antlr3PostProcess" classpath="Your Classpath Here">
            <classpath><path refid="antlr.3" /><path refid="string.template" /></classpath>
</taskdef>

Reference the task after the Antlr has generated the Java files, but before javac.

<replace file="${antlr3.output}/Db2Parser.java" token="public static final String[] tokenNames" value="public final String[] tokenNames"/>
<replace file="${antlr3.output}/Db2Parser.java" token="Db2Parser.tokenNames" value="tokenNames"/>
<Antlr3PostProcess oldTarget="${antlr3.output}/Db2Parser.java" pkg="oracle.dbtools.migration.parser.grammar.antlr3">
</Antlr3PostProcess>