$//$CAB$301$ Assignment $2$

$//$ToolCollection ADT specification

using System;

$//$ Invariants: no duplicate tools in this tool collection $($all the tools in this tool collection have different names$)$ and the number of tools in this tool collection is greater than equals to $0$

interface IToolCollection

$\{$

$//$ get the number of tools in this tool collection

int Number

$\{$

get;

$\}$

$//$ Check if this tool collection is empty

$//$ Pre$-$condition: nil

$//$ Post$-$condition: return true if this tool collection is empty; otherwise, return false. This tool collection remains unchanged and new Number $=$ old Number

bool IsEmpty$()$;

$//$ Insert a new tool into this tool collection

$//$ Pre$-$condition: the new tool is not in this tool collection

$//$ Post$-$condition: the new tool is added into this tool collection, new Number $=$ old Number $+1$ and return true; otherwise, the new tool is not added into this tool collection, new Number $=$ old Number and return false.

bool Insert$($ITool tool$)$;

$//$ Delete a tool from this tool collection

$//$ Pre$-$condition: nil

$//$ Post$-$condition: the tool is removed out of this tool collection, new Number $=$ old Number $-1$ and return true, if the tool is present in this tool collection;

$//$ otherwise, this tool collection remains unchanged, and new Number $=$ old Number, and return false, if the tool is not present in this tool collection.

bool Delete$($ITool tool$)$;

$//$ Search for a tool by its name in this tool collection

$//$ pre: nil

$//$ post: return the reference of the tool object if the tool is in this tool collection;

$//$ otherwise, return null. New Number $=$ old Number.

ITool? Search$($string toolName$)$;

$//$ Return an array that contains all the tools in this tool collection and the tools in the array are sorted in the dictionary order by their names

$//$ Pre$-$condition: nil

$//$ Post$-$condition: return an array that contains all the tools in this tool collection and the tools in the array are sorted in alphabetical order by their names and new Number $=$ old Number.

ITool$[]$ ToArray$()$;

$//$ Clear this tool collection

$//$ Pre$-$condition: nil

$//$ Post$-$condition: all the tools in this tool collection are removed from this tool collection and Number $=0.$

void Clear$()$;

$\}$