Complete the TODO in below java code: package heapdb;

import java.util.Iterator;

import java.util.ArrayList;

import java.nio.ByteBuffer;

public class TableHeap implements ITable $\{$

BlockedFile bfile;

Schema schema;

BitMap bitmap; $//0=$free, $1=$row

int rows$\_$per$\_$block;

Index$[]$ indexes;

public TableHeap$($String filename, Schema schema$)\{$

this.schema $=$ schema;

$//$ create a new file

$//$ write schema to block $0$

$//$ write free space bitmap to block $1$

$//$ data rows start at block $2$

bfile $=$ new BlockedFile$($filename$,$ true$)$;

ByteBuffer buffer $=$ ByteBuffer.wrap$($new byte$[4096])$;

buffer.position$(8)$;

schema.serialize$($buffer$)$;

$//$ set bytes used in the buffer.

buffer.putInt$(0,$ buffer.position$())$;

bfile.writeBlock$(0,$ buffer$)$;

$//$ write out BitMap of all $0\text{'}$s

bitmap $=$ new BitMap$()$;

bfile.writeBlock$(1,$ bitmap.getBytes$())$;

rows$\_$per$\_$block $=(4096-8)/$schema$.$getTupleSizeInBytes$()$;

indexes $=$ new Index$[$schema$.$size$()]$;

$\}$

public TableHeap$($String filename$)\{$

$//$ open existing file

bfile $=$ new BlockedFile$($filename$,$ false$)$;

$//$ read the schema from block $0$

ByteBuffer buffer $=$ ByteBuffer.wrap$($new byte$[4096])$;

bfile.readBlock$(0,$ buffer$)$;

buffer.limit$($buffer$.$getInt$(0))$;

buffer.position$(8)$;

schema $=$ Schema.deserialize$($buffer$)$;

$//$ read the bitmap from block $1$

byte$[]$ bytes $=$ new byte$[4096]$;

bfile.readBlock$(1,$ bytes$)$;

bitmap $=$ new BitMap$($bytes$)$;

rows$\_$per$\_$block $=(4096-8)/$schema$.$getTupleSizeInBytes$()$;

indexes $=$ new Index$[$schema$.$size$()]$;

$\}$

@Override

public void close$()\{$

if $($bfile$.$isOpen$())\{$

$//$ write the bitmap

bfile.writeBlock$(1,$ bitmap.getBytes$())$;

bfile.close$()$;

$\}$

$\}$

@Override

public Iterator iterator$()\{$

return new TupleIterator$()$;

$\}$

public class TupleIterator implements Iterator $\{$

private int row$\_$no $=-1$;

private int current$\_$block$\_$no $=0$;

private ByteBuffer buffer $=$ ByteBuffer.wrap$($new byte$[4096])$;

@Override

public boolean hasNext$()\{$

for $($row$\_$no$=$row$\_$no$+1$; row$\_$no$<4096*8$; row$\_$no$++)\{$

if $($bitmap$.$getBit$($row$\_$no$))\{$

return true;

$\}$

$\}$

return false;

$\}$

@Override

public Tuple next$()\{$

$//$ read row

int block$\_$no $=$ row$\_$no$/$rows$\_$per$\_$block $+2$;

int offset $=($row$\_$no$\%$rows$\_$per$\_$block$)*$ schema.getTupleSizeInBytes$()$;

$//$ read the block

if $($current$\_$block$\_$no $!=$ block$\_$no$)\{$

$//$ read the block

bfile.readBlock$($block$\_$no$,$ buffer$)$;

current$\_$block$\_$no $=$ block$\_$no;

$\}$

$//$ get the tuple

buffer.position$($offset$)$;

Tuple t $=$ Tuple.deserialize$($schema$,$ buffer$)$;

return t;

$\}$

private int getRowNo$()\{$

return row$\_$no;

$\}$

$\}$

@Override

public Schema getSchema$()\{$

return schema;

$\}$

$/*$

$*$ return the number of rows in table

$*/$

@Override

public int size$()\{$

int size$=0$;

for $($int i$=0$; i