public static CompilerAdapter getCompiler(String compilerType,
    Task task) throws BuildException 
{
            boolean isClassicCompilerSupported = true;
            //as new versions of java come out, add them to this test
            if (!JavaEnvUtils.isJavaVersion(JavaEnvUtils.JAVA_1_2)
                && !JavaEnvUtils.isJavaVersion(JavaEnvUtils.JAVA_1_3)) {
                isClassicCompilerSupported = false;
            }
            if (compilerType.equalsIgnoreCase("jikes")) {
                return new Jikes();
            }
            if (compilerType.equalsIgnoreCase("extJavac")) {
                return new JavacExternal();
            }
            if (compilerType.equalsIgnoreCase("classic")
                || compilerType.equalsIgnoreCase("javac1.1")
                || compilerType.equalsIgnoreCase("javac1.2")) {
                if (isClassicCompilerSupported) {
                    return new Javac12();
                } else {
                    task.log("This version of java does "
                                             + "not support the classic "
                                             + "compiler; upgrading to modern",
                                             Project.MSG_WARN);
                    compilerType = "modern";
                }
            }
            //on java< =1.3 the modern falls back to classic if it is not found
            //but on java >=1.4 we just bail out early
            if (compilerType.equalsIgnoreCase("modern")
                || compilerType.equalsIgnoreCase("javac1.3")
                || compilerType.equalsIgnoreCase("javac1.4")
                || compilerType.equalsIgnoreCase("javac1.5")
                || compilerType.equalsIgnoreCase("javac1.6")) {
                // does the modern compiler exist?
                if (doesModernCompilerExist()) {
                    return new Javac13();
                } else {
                    if (isClassicCompilerSupported) {
                        task.log("Modern compiler not found - looking for "
                                 + "classic compiler", Project.MSG_WARN);
                        return new Javac12();
                    } else {
                        throw new BuildException("Unable to find a javac "
                                                 + "compiler;\n"
                                                 + MODERN_COMPILER
                                                 + " is not on the "
                                                 + "classpath.\n"
                                                 + "Perhaps JAVA_HOME does not"
                                                 + " point to the JDK.\n"
                                + "It is currently set to \""
                                + JavaEnvUtils.getJavaHome()
                                + "\"");
                    }
                }
            }
            if (compilerType.equalsIgnoreCase("jvc")
                || compilerType.equalsIgnoreCase("microsoft")) {
                return new Jvc();
            }
            if (compilerType.equalsIgnoreCase("kjc")) {
                return new Kjc();
            }
            if (compilerType.equalsIgnoreCase("gcj")) {
                return new Gcj();
            }
            if (compilerType.equalsIgnoreCase("sj")
                || compilerType.equalsIgnoreCase("symantec")) {
                return new Sj();
            }
            return resolveClassName(compilerType);
}

Based on the parameter passed in, this method creates the necessary factory desired. The current mapping for compiler names are as follows:
• jikes = jikes compiler
• classic, javac1.1, javac1.2 = the standard compiler from JDK 1.1/1.2
• modern, javac1.3, javac1.4, javac1.5 = the compiler of JDK 1.3+
• jvc, microsoft = the command line compiler from Microsoft's SDK for Java / Visual J++
• kjc = the kopi compiler
• gcj = the gcj compiler from gcc
• sj, symantec = the Symantec Java compiler
• a fully qualified classname = the name of a compiler adapter