Csc 1302, Honors Principles of Computer Science II (Fall 2021)

Week 2 (3 September 2021)

Initialize Database from Files; Check Equality of Tuples; Remove Duplicates in Relation

During this week you will write the following methods:

1. Initialize Database object by reading data stored in several files in a directory that is given in command line (this method belongs to Database.java)

   //Create the database object by reading data from several files in directory dir
   public void initializeDatabase(String dir) {
   
   }
   

   Here is a sample of files available in the directory: drinks (also in .zip format: drinks.zip). The file catalog.dat contains schema information for all the relations in the database and individual .dat files contain the relation instances (tuples).

   To read data from a file, you can use the following code:

   FileInputStream fin1 = null;
   BufferedReader infile1 = null;
   try {
     fin1 = new FileInputStream("f.dat");
     infile1 = new BufferedReader(new InputStreamReader(fin1));
     String s = infile1.readLine();
     ...
     ...
     fin1.close();
   } catch (IOException e) {
       System.out.println("Error reading file");
     }
   

2. Test equality of tuples (this method belongs to Tuple.java)

   // Return true if this tuple is equal to compareTuple; false otherwise
   public boolean equals(Tuple compareTuple) {
   
   }
   

3. Remove duplicate tuples (this method belongs to Relation.java)

   // Remove duplicate tuples from this relation
   public void removeDuplicates() {
   
   }
   

Download the Driver Programs and implement all the methods in these Java classes. Compile and run the driver programs.

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You should see the following output when you run Driver2.java:

[raj@tinman w2]$ java Driver2 drinks
Database Schema
-------- ------

SERVES(BNAME:VARCHAR,RNAME:VARCHAR)
BAR(BNAME:VARCHAR)
SELLS(BAR:VARCHAR,BEER:VARCHAR,PRICE:INTEGER)
DRINKER(DNAME:VARCHAR)
LIKES(DNAME:VARCHAR,RNAME:VARCHAR)
FREQUENTS(DNAME:VARCHAR,BNAME:VARCHAR)
BARS(NAME:VARCHAR,ADDR:VARCHAR)
BEER(RNAME:VARCHAR,PRICE:INTEGER)

BAR(BNAME:VARCHAR)
Number of tuples: 4

Jillians:
Dugans:
ESPN Zone:
Charlies:

DRINKER(DNAME:VARCHAR)
Number of tuples: 5

John:
Peter:
Donald:
Jeremy:
Clark:

SELLS(BAR:VARCHAR,BEER:VARCHAR,PRICE:INTEGER)
Number of tuples: 9

Jillians:Bud:6:
Jillians:Michelob:6:
Jillians:Heineken:8:
Dugans:Bud:9:
Dugans:Michelob:10:
Dugans:Fosters:12:
ESPN Zone:Fosters:9:
Charlies:Heineken:10:
Charlies:Foster:10:

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and the following output when you run the DuplicatesDriver.java program:

[raj@tinman w2]$ java DuplicatesDriver
Before Removing Duplicates: 
STUDENT(SID:INTEGER,SNAME:VARCHAR)
Number of tuples: 7

1111:Robert Adams:
1112:Charles Bailey:
1113:Donald James:
1112:Charles Bailey:
1112:Charles Bailey:
1114:Michael James:
1113:Donald James:

After Removing Duplicates: 
STUDENT(SID:INTEGER,SNAME:VARCHAR)
Number of tuples: 4

1111:Robert Adams:
1112:Charles Bailey:
1113:Donald James:
1114:Michael James:

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