URGENT Can someone help me solve this problem in java?

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In this assignment, you will write a HashTable class and a TestHashTable class.

The HashItem Class

Here is the UML diagram for HashItem:

UML diagram showing attributes and methods for HashItem

There is no setKey$()$ method, because if the key were to change, it would be a different item altogether. I am providing this code for you. Here is the code that you will use. Download Here is the code that you will use. Do not modify this file!

The HashTable Class

Here is the UML diagram for HashTable.

UML diagram showing class name, properties, and methods

The properties are as follows:

nSlots

The number of slots in the table; this is set by the constructor.

size

The number of items in the table. This allows users to retrieve the total in an O$(1)$ operation.

slots

This is an ArrayList$>>$; that is$,$ an ArrayList of ArrayList. Each item in the outer ArrayList represents a slot; the inner ArrayList contains those HashItems with the corresponding hash code $($slot number$)$

The properties are all public to make them easier to access outside the class.

The constructor takes one parameter: the number of slots in the HashTable. The constructor should use this parameter to build the initial slots attribute. You can leave the inner ArrayLists as null, or you can create an empty ArrayList for each slot. The former is quicker, the latter may make your other code a bit easier. The constructor also sets the size attribute to zero.

The private hashFunction$()$ method takes a key object and returns an integer in the range $[0..$nSlots$).$ How can you get a hash code for any arbitrary object? The answer is to use the key$$s hashCode$()$ method. Every Object has this method built in; see the documentation Links to an external site.. Note: the built$-$in hashCode$()$ method may return a negative number.

The put$()$ method inserts the given key and value into the table if the key isn$$t already in the table. If the key already exists in the table, the value is changed. $($Remember that keys must be unique.$)$

The get$()$ method takes a key as its parameter and returns the corresponding value, or null if the key is not in the table.

The private getItem$()$ method takes a key as its parameter and returns the corresponding key$-$and$-$value HashItem, or null if the key is not in the table. This is an optional method. You do not have to implement it$,$ but you might find it to be very useful to avoid duplicated code in get$()$ and put$().$

Finally, the getSize$()$ and getNSlots$()$ retrieve the number of items and number of slots in the table; toString returns a String representation of the hash table.

The TestHashTable Class

Write a Java class named TestHashTable with a main$()$ method that does the following:

Creates a HashTable named cityTable. Give it as many $($or as few$)$ slots as you like.

Opens a file of city information. Here is a large file Download Here is a large file, and here is a smaller file Download here is a smaller file that you can use for testing. Note: The large file has one city name that is duplicated $($on lines $289$ and $292).$ This is probably a typographical error in the original file, but I am leaving it in because it is a good test to see that your put$()$ method works properly when given an entry that is already in the table.

Reads the file and enters each city and population into the table.

Prints the number of entries in the table.

Displays how many items are in each slot of the table.

Repeatedly asks the user for a city name. If the city is in the table, the program displays the population; otherwise, it says the city is not found.

Here is the starting point for the TestHashTable program. Download Here is the starting point for the TestHashTable program.

Sample Output

Here$$s the output from the program using $20$ slots $($I have omitted some lines to save space$).$ Your output does not have to match this example exactly, but it should contain similar information:

Entries in table: $354$

Slot $0$ has $17$ items.

Slot $1$ has $18$ items.

Slot $2$ has $20$ items.

Slot $3$ has $17$ items.

$...$

Slot $17$ has $17$ items.

Slot $18$ has $20$ items.

Slot $19$ has $13$ items.

Type a city name, or press ENTER to quit: Paris

Paris has population $2,138,551.$

Type a city name, or press ENTER to quit: Duluth

Duluth not found.

Type a city name, or press ENTER to quit: Bangalore

Bangalore has population $5,104,047.$

Type a city name, or press ENTER to quit: