Class Head

java.lang.Object
  |
  +--Command
        |
        +--Head

public class Head

extends Command

The Head class (a subclass of the abstract base class Command) implements the familiar unix command head, which outputs the first number of lines of each file. This class implements the abstract methods execute and getDescription inherited from the abstract base class Command.

Field Summary

protected java.util.Vector	fileList A vector containing string arguments to head - i.e. filenames.
protected int	numLinesToRead An int value containing the number of lines to read from file.
protected java.util.Vector	numList A vector containing numerical arguments to head.

Constructor Summary

Head()

Method Summary

java.lang.String	execute(java.lang.String args) Executes the head command and returns the result in the form of a String object.
protected java.lang.String	fileToString(java.lang.String filename) A helper function that converts the given file to a String object containing the number of lines specified by numLinesToRead.
java.lang.String	getDescription() Returns a description of the command.
protected void	processArgs(java.lang.String argLine) A helper function that parses the arguments of this command into appropriate containers.

Methods inherited from class Command

ExpandArgs

Methods inherited from class java.lang.Object

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

Field Detail

numList

protected java.util.Vector numList

A vector containing numerical arguments to head.

fileList

protected java.util.Vector fileList

A vector containing string arguments to head - i.e. filenames.

numLinesToRead

protected int numLinesToRead

An int value containing the number of lines to read from file.

Constructor Detail

Head

public Head()

Method Detail

execute

public java.lang.String execute(java.lang.String args)

Executes the head command and returns the result in the form of a String object.

Specified by:

execute in class Command

Parameters:

args - arguments for this command.

Returns:

the string result of executing the head command.

fileToString

protected java.lang.String fileToString(java.lang.String filename)

A helper function that converts the given file to a String object containing the number of lines specified by numLinesToRead.

Parameters:

filename - name of file to be converted to a string.

Returns:

a string containing the contents of the specified file.

processArgs

protected void processArgs(java.lang.String argLine)

A helper function that parses the arguments of this command into appropriate containers.

Parameters:

argLine - arguments to be parsed.

getDescription

public java.lang.String getDescription()

Description copied from class: Command

Returns a description of the command.

Specified by:

getDescription in class Command

Returns:

the name of the command.