if we are fortunateand our program has no syntax errorsthen this compilation process will create files with classextension if our program contains syntax errorsthen these will be identifiedand we will have to go back into our editor to fix the offending lines of code once we have eliminated all syntax errorsand created the appropriate compiled codewe can run our program by either invoking commandsuch as "java(outside an ide)or by clicking on the appropriate "runbutton (within an idewhen java program is run in this waythe run-time environment locates the directories containing the named class and any other classes that are referenced from this class according to special operating system environment variable this variable is named "classpath,and the ordering of directories to search in is given as list of directorieswhich are separated by colons in unix/linux or semicolons in dos/windows an example classpath assignment in the dos/windows operating system could be the followingset classpath; :\java; :\program files\javawhereas an example classpath assignment in the unix/linux operating system could be the followingsetenv classpath :/usr/local/java/lib:/usr/netscape/classesin both casesthe dot ("refers to the current directory in which the run-time environment is invoked javadoc in order to encourage good use of block comments and the automatic production of documentationthe java programming environment comes with documentation production program called javadoc this program takes collection of java source files that have been commented using certain keywordscalled tagsand it produces series of html documents that describe the classesmethodsvariablesand constants contained in these files for space reasonswe have not used javadocstyle comments in all the example programs included in this bookbut we include javadoc example in code fragment as well as other examples at the web site that accompanies this book each javadoc comment is block comment that starts with "/**and ends with "*/,and each line between these two can begin with single asterisk"*,which is ignored the block comment is assumed to start with descriptive sentencefollowed by blank linewhich is followed by special lines that begin with javadoc tags block comment that comes just before class definitioninstance