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PLEASE COMMENT ON THE CODE AS WELL.
HOUSEDATA.BIN
*117 E 26th Ave, Ellensburg, WA 98926
Þ ‘È nThis is a beautiful ranch rambler home with a great
location near the college.
*1106 N Canterbury Dr, Ellensburg, WA 98926b d¸ n3
Bedroom ,2 bathroom 1890 sq. ft. Net Zero Energy Home. R30 exterior
walls R50 ceiling.
*1 Brick Mill Rd, Ellensburg, WA 98926
§ wÜ nHorse ready w/sand filled arena, 2 stall horse
shed w/tack room, 3 stall barn for extra parking & hay storage.
*11867 56th Pl S, Seattle, WA 98178 J î
nThe open concept brings in natural light, highlighting the quality
and taste in the finishes.
*3112 E Laurelhurst Dr NE, Seattle,WA
98105Ô }â nRare opportunity to own 65' of coveted Laurelhurst
waterfront. Expansive Lake & Mtn views from all levels.
Introduction We've discussed in lecture, what binary files are and how to work with them in Java. For this lab you will be provided a binary file which contains some information about a few house listed for sale. For each house there will be an address, number of bedrooms, square footage, price, and a short description about the house. To get started download the following file from Canvas: • HouseData.bin HouseData.bin is a binary file. You can try opening it in a Notepad but you will only see some of the information stored in the file. It is not a text file, but rather a binary file. Some of the information stored in the binary file is text, even though it is stored in binary format, you will be able to see the characters. This is because when a character is being stored it is converted to a decimal equivalent Unicode number, which is then encoded in binary, Text editors to the reverse of it to show us characters. The file has the following structure for each entry (house record): o Address - 44 bytes total Num bedrooms - 1 byte o o Square footage - 2 bytes Price - 4 bytes o o Description - 112 bytes Address and description were written with method write UTF(). Address is originally 42 bytes long, but the method added 2 additionally bytes in the begging to specify how many bytes belong to this string. If you use the method readUTF() to read the address information, you don't have to worry about those two bytes. In this lab you will read all bytes from the file and print out the information. There are several distinct house "entries" in the file. You will also write a method, which will update the price for each house by a certain percentage. Write a java class named ReadHouseData This class should have the main method and two additional methods. A method named printOutHouseData(), which takes a single parameter of type String representing the file name. This method will read the bytes from the file and print out house records. The second method should be named increasePrice(), which also takes in a file name and an additional int value. The class RandomAccessFile allows us to move the file pointer to any location in the file. Using the class Random Access File in the method increasePrice(), you will update the price for each house record. More information about each method is available below.
I. printOutHouseData() Using DataInputStream with FileInputStream read the binary file. Have a look at the lecture slides on how to set this up, if you don't remember. There are several methods in the DataInputStream which can be used to read the file. Have a look at the API. To read the address, you can use the method readUTFO). To read the square footage, you can use the method readShort(). The numbers of bedrooms is stored as a single byte. Check which method can be used to read a single byte and represent a number. Also check which method can read 4 bytes and represent a number for the price of the house. It is crucial to read the information from the file in the correct order. Otherwise you will not get the desired output. Have a look on the previous page at the file structure. As you are reading the information and printing it out, add brief text to each print out. For example when you print out the number of bedrooms, you can add text like "Number of bedrooms : ". Have a look at the sample output in Figure 1. II. increase Price() The method increase Price() should take in two parameters, a file name and an integer, to specify a percent value by which the price should be increased. In this method open the binary file using the Random AccessFile class, in "rw" mode. Refer to the lecture slides for examples if needed. Random AccessFile class has the same methods as DataInputStream and DataOutputStream. Additionally it also has a few other methods, one of them being seek(). The seek() method takes in an integer value, and places the file pointer at the location of the integer value. When reading/writing is being performed, it is always done at the location of the file pointer. By looking at the file structure (number of bytes for each piece of information) you can calculate at which byte location the price for the first house is stored. Do the following inside a loop: 1. Using the method seek(), you can move the file pointer to the location of the first byte for the price of the first house. 2. Read the price, and increase it by the percent value getting passed into the method. 3. Move the file pointer back to the beginning of the price you just read. 4. Write to the file the updated price. 5. Move the pointer to the next house entry in the file. (You will need to calculate the number of bytes to move the file pointer.)
If the steps mentioned above are done properly, the prices should be updated without corrupting the file. III. main() This method is very short and can be written in 7 lines of code, not including comments or line breaks. In the main method do the following: 1. Call the method printOutHouseData() passing to it the name of the file. 2. Prompt the user and retrieve a value for percent by which the house prices should be increased. 3. Call the method increasePrice() passing to it the file name and the percent value. 4. Print out some text to separate the next set of print statements, could be something like "updating prices" or just a few line breaks. 5. Call the method printOutHouseData() once more.
IV. Sample Output Sample output of the program can be seen below on Figure 1 and Figure 2. ----jGRASP exec: java ReadHouseData Address: 117 E 26th Ave, Ellensburg, WA 98926 Number of bedrooms: 4 Square feet 2014 Price USD 365000 This is a beautiful ranch rambler home with a great location near the college. ************* Address: 1106 N Canterbury Dr, Ellensburg, WA 98926 Number of bedrooms : 3 Square feet 1890 Price USD 419000 3 Bedroom , 2 bathroom 1890 sq. ft. Net Zero Energy Home. R30 exterior walls R50 ceiling. ***** How many percent would you like to incease the house prices by? 10 Address: 117 E 26th Ave, Ellensburg, WA 98926 Number of bedrooms: 4 Square feet 2014 Price USD 401500 This is a beautiful ranch rambler home with a great location near the college. *** Figure 1 Sample Output