Class Shell

java.lang.Object

Shell

Direct Known Subclasses:

AssignX

public class Shell
extends java.lang.Object

This is a base class for several assignments you will write. Do NOT change anything in this file. Its purpose it to executes commands, one command per line. Commands may be entered via the keyboard or read from a file. It contains a variey of utility routines to make it easy to enter for null values and to enter arrays (String/int) as a list of comma separated values.

In writing your code, you may be tempted to use System.out.println() to determine what is happening. As an alternative, the method debug() is provided. The nice thing about debug() in comparison to System.out.println() is that debug() only prints when debug is turn on. You can turn debug on and off by giving the debug command to this program. Thus, you can write debug code, but not need to change your program in any way before turning it in. If you use System.out.println() you MUST either comment out the lines or remove them before you submit your code for grading. This is a simple alternative to the many logging packages that have more advanced capabilities. See this page for examples.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private static class	Shell.StopProcessing A class to help end processing that is only used internally by Shell.

Field Summary

Fields

Modifier and Type	Field and Description
protected static int	debug Any non-zero value turns debugging on
private static java.util.Random	random Random number generator

Constructor Summary

Constructors

Constructor and Description
Shell()

Method Summary

Modifier and Type	Method and Description
static void	debug(java.lang.String format, java.lang.Object... args) Print a message if the debug value is non-zero.
protected java.lang.String	filter(java.lang.String input) Filter input for some special cases.
static java.lang.String	format(java.lang.String format, java.lang.Object... args) An "extension" of String.format() to automatically convert arrays to Strings using the Arrays.toString() methods.
int[]	getIntArray(java.util.Scanner scanner) Get an array of int separated by commas from the scanner.
static java.util.Random	getRandom() Get the shells random number generator.
java.lang.String[]	getStrArray(java.util.Scanner scanner) Get an array of String separated by commas from the scanner.
java.lang.String	getStringOrNull(java.util.Scanner scanner) Retrieve a String from the scanner, filtering it for convenience.
static void	main(java.lang.String[] args) Entry point to shell.
void	ooMain(java.lang.String[] args) Provide a main() like method that can be inherited and/or overridden.
void	processCmdsFromFile(java.lang.String fileName) Process commands from a file.
void	processCommands() Process commands from System.in.
void	processCommands(java.util.Scanner scanner) Command interpreter to test code.
void	processOneCommand(java.lang.String cmd, java.lang.String params) Process one command.
java.lang.String	rest(java.util.Scanner scanner) Retrieve a String from the scanner using nextLine(), to get everything else in the line and filter it for special values.
void	showHelp() Display a brief help summary for commands implemented by this class
int[]	strArrayToIntArray(java.lang.String[] strResult) Convert an array of String to an array of int.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

debug

protected static int debug

Any non-zero value turns debugging on

random

private static java.util.Random random

Random number generator

Constructor Detail

Shell

public Shell()

Method Detail

format

public static java.lang.String format(java.lang.String format,
                                      java.lang.Object... args)

An "extension" of String.format() to automatically convert arrays to Strings using the Arrays.toString() methods. Arrays of arrays are also handled. The argument list is exactly the same as that of String.format(), so any of the features of that code may be used. If there is only a single argument after the format and if that argument is an array, cast it to an Object using ((Object))

Parameters:

format - - the format string for the output (use %s for arrays)

args - - argments for the format string (variable number)

debug

public static void debug(java.lang.String format,
                         java.lang.Object... args)

Print a message if the debug value is non-zero. The argument list is exactly the same as that of String.format(), so any of the features of that code may be used. See the documentation of Shell.format() for details on printing arrays.

Parameters:

format - - the format string for the output

args - - argments for the format string (variable number)

getRandom

public static java.util.Random getRandom()

Get the shells random number generator. If one has not yet been created, create one. To get repeatable results, use the random command with a seed.

showHelp

public void showHelp()

Display a brief help summary for commands implemented by this class

filter

protected java.lang.String filter(java.lang.String input)

Filter input for some special cases.

Parameters:

input - - the original string

Returns:

The string is trimmed. If it is the String "empty!", return "". If it is the String "null!", return null. Otherwise, return the trimmed String. Override this for more special conditions.

getStringOrNull

public java.lang.String getStringOrNull(java.util.Scanner scanner)

Retrieve a String from the scanner, filtering it for convenience. A future enhancement will include quoting so that a "parameter" may have embedded blanks, quotes, etc.

Parameters:

scanner - - retrieve String from this Scanner.

Returns:

the filtered String (possibly null).

rest

public java.lang.String rest(java.util.Scanner scanner)

Retrieve a String from the scanner using nextLine(), to get everything else in the line and filter it for special values. This differs from Scaner.nextLine() in that the reult is trimmed of leading and trailing blanks, and the special string null!null and empty!"".

Parameters:

scanner - - retrieve String from this Scanner.

Returns:

the trimmed, filtered String (possibly null).

getStrArray

public java.lang.String[] getStrArray(java.util.Scanner scanner)

Get an array of String separated by commas from the scanner. A future enhancement will allow quoting so that individual elements may contain escaped commas.

Parameters:

scanner - - source of the array

Returns:

an array (possibly null, containing the filtered values.

getIntArray

public int[] getIntArray(java.util.Scanner scanner)

Get an array of int separated by commas from the scanner.

Parameters:

scanner - - source of the array

Returns:

an array (possibly null, containing the values

strArrayToIntArray

public int[] strArrayToIntArray(java.lang.String[] strResult)

Convert an array of String to an array of int.

Parameters:

strResult - - array of Strings to be converted to ints

Returns:

Each String is converted to an int

processOneCommand

public void processOneCommand(java.lang.String cmd,
                              java.lang.String params)
                       throws java.io.FileNotFoundException,
                              java.util.NoSuchElementException

Process one command.

Parameters:

cmd - - the command to process

params - - a string containing the parameter(s) (if any)

Throws:

java.io.FileNotFoundException

java.util.NoSuchElementException

processCommands

public void processCommands(java.util.Scanner scanner)

Command interpreter to test code. Process the commands where each command is contained on a separate line. End-of-line comments begin with '#'. Comments are removed and the resulting string trimmed. Empty lines are ignored.

Parameters:

scanner - - the source of the commands

processCmdsFromFile

public void processCmdsFromFile(java.lang.String fileName)

Process commands from a file.

Parameters:

fileName - - name of file containing commands

processCommands

public void processCommands()

Process commands from System.in.

ooMain

public void ooMain(java.lang.String[] args)

Provide a main() like method that can be inherited and/or overridden.

Parameters:

args - - arguments to process. If args is null or of length 0, commands are taken from System.in. If args.length > 0, the args are assumed to be one or more file to be processed using the input command..

main

public static void main(java.lang.String[] args)

Entry point to shell.

Parameters:

args - - an array of Strings