SORTING - Introduction to Java Programming: Comprehensive Version - page 887

26 else {
27 intFromF2 = f2.readInt();
28 }
29 }
30 }
31
32 while (f1.available() > 0 && f1Count++ < segmentSize) {
33 f3.writeInt(f1.readInt());
34 }
35
36 while (f2.available() > 0 && f2Count++ < segmentSize) {
37 f3.writeInt(f2.readInt());
38 }
39 }

remaining f1 segment

remaining f2 segment

23.8.3 Combining Two Phases
Listing 23.16 gives the complete program for sorting int values in largedata.dat and storing
the sorted data in sortedfile.dat .

L ISTING 23.16

SortLargeFile.java
1 import java.io.*;
2
3 public class SortLargeFile {
4

public static final int MAX_ARRAY_SIZE = 100000 ;

max array size
I/O stream buffer size

5 public static final int BUFFER_SIZE = 100000 ;

6
7 public static void main(String[] args) throws Exception {
8 // Sort largedata.dat to sortedfile.dat
9 sort( "largedata.dat" , "sortedfile.dat" );
10
11 // Display the first 100 numbers in the sorted file
12 displayFile( "sortedfile.dat" );
13 }
14
15 /** Sort data in source file into target file */

16 public static void sort(String sourcefile, String targetfile)

17 throws Exception {

18 // Implement Phase 1: Create initial segments

19 int numberOfSegments =

20 initializeSegments(MAX_ARRAY_SIZE, sourcefile, "f1.dat" );

create initial segments

21
22 // Implement Phase 2: Merge segments recursively

23 merge(numberOfSegments, MAX_ARRAY_SIZE, merge recursively

24 "f1.dat" , "f2.dat" , "f3.dat", targetfile );

25 }
26
27 /** Sort original file into sorted segments */
28 private static int initializeSegments
29 ( int segmentSize, String originalFile, String f1)
30

throws Exception {

31 // Same as Listing 23.12, so omitted

32 }
33
34 private static void merge( int numberOfSegments, int segmentSize,
35 String f1, String f2, String f3, String targetfile)
36

throws Exception {

37 if (numberOfSegments > 1 ) {

38 mergeOneStep(numberOfSegments, segmentSize, f1, f2, f3); merge one step