private String getHeader() {
        return "// ------------   D O   N O T   E D I T !   ------------\n" + //
               "// This file is generated from a config definition file.\n" + //
               "\n" + //
               "package " + javaPackage + ";\n" + //
               "\n" + //
               "import java.util.*;\n" + //
               "import java.io.File;\n" + //
               "import java.nio.file.Path;\n" + //
               "import com.yahoo.config.*;";
    }
Builds one Java class based on the given CNode tree.

@author gjoranv
@author Tony Vaagenes
@author ollivir
configgen/src/main/java/com/yahoo/config/codegen/JavaClassBuilder.java