tablescan.java

this a program for for database implement in this we are implementing several join algorithms

/*Class for table scan Iterator
    Methods:-
	Open()
	GetNext()
	Close()
We are assuming block size is 2
	*/
import java.io.*;
import java.util.*;
import java.lang.*;
public class TableScan
	{
		int BlockSize=2;
		String[][] mainMemory=new String[50][50];
		String[] AllAttributes=new String[50];
		
		//For Processing
		int BlockPointer;
		int TuplePointer;
		String[][] Buffer=new String[20][20];
		
		//Some Constants
		int NumOfAttributes=0;
		int NumOfTuples=0;
		
		String Relation;
		String Filename;
		
		public TableScan()
		{
		this(null,null);
		}
		
		public TableScan(String R,String file)
		{
		Relation=R;
		Filename=file;
		System.out.println("File : "+Filename);
		LoadFile(Filename);
		}
			//Reading Files

		String[] ReadFile(String file) 
		{
			String[] file_data=new String[100];
			try{
				BufferedReader is = new BufferedReader(new FileReader(file));
				String inputLine;

				int i=0;
				while ((inputLine = is.readLine()) != null) 
				{
					file_data[i]=inputLine.toString();
					i++;
				}
				is.close();

				} catch (IOException e) 
					{
						System.out.println("IOException: " + e);
					}

			return file_data;
		}
			//tokenize
		String[] Tokenize(String S)
		{
			String[] result = S.split("\\s");
			return result;
		}
			//Loading Data
		void LoadFile(String file)
		{
			String[] Table=ReadFile(file);
			String[] Attributes=Tokenize(Table[0]);
			NumOfAttributes=Attributes.length;
			
			for(int i=0;i<NumOfAttributes;i++)
			{
				AllAttributes[i]=Attributes[i];
			}
			
			int pointer=0;
			while(pointer<50 && Table[pointer+1]!=null)
			{
				String[] temp=Tokenize(Table[pointer+1]);
				for(int i=0;i<NumOfAttributes;i++)
				{
					mainMemory[pointer][i]=temp[i];
				}
				pointer++;
			}
			NumOfTuples=pointer;
		}
			//Printing Data
		void PrintRelation()
		{
			System.out.println("Relation name : "+Relation);
			System.out.println("No of Attributes : "+NumOfAttributes);
			System.out.println("No of Tuples : "+NumOfTuples);
			System.out.println("Table : ");
			for(int i=0;i<NumOfAttributes;i++)
			{	
				System.out.print(AllAttributes[i]+" ");
			}
			System.out.println();
			
			for(int i=0;i<NumOfTuples;i++)
			{
				for(int j=0;j<NumOfAttributes;j++)
				{
					System.out.print(mainMemory[i][j]+" ");
				}
				System.out.println();
			}
		}
		void PrintTuple(String[] t)
		{
			for(int i=0;i<t.length;i++)
			{
				System.out.print(t[i]+" ");
			}
			System.out.println();
		}
			//Iterator Functions
		void Open()
		{
			BlockPointer=0;
			TuplePointer=0;
		}
		String[] GetNext()
		{
			String[] tuple=new String[NumOfAttributes];
			if(TuplePointer==BlockSize)
			{
				BlockPointer=BlockPointer+BlockSize;
				if(BlockPointer>NumOfTuples)
				{
					return null;
				}
				else
				{
					TuplePointer=0;
				}
			}
			for(int i=0;i<NumOfAttributes;i++)
			{
				tuple[i]=mainMemory[BlockPointer+TuplePointer][i];
			}
			TuplePointer++;
			
			if(tuple[0]==null)
				return null;
			else
				return tuple;
		}
		
		void Close()
		{
		//System.out.println("Iterator TableScan for "+Relation+" is Closed !");
		}
		
		//main function 
		/*
		public static void main(String args[])
		{
			TableScan R=new TableScan("R","R.txt");
			R.PrintRelation();
			System.out.println("\n");
		
			R.Open();
			String[] tuple=R.GetNext();
			while(tuple!=null)
			{
				R.PrintTuple(tuple);
				tuple=R.GetNext();
			}
			R.Close();
		}
		*/
	}