Working with Files - Advanced Topics in Java: Core Concepts in Data Structures - page 207

Index[] index = retrieveIndex();
int numRecords = index[0].recNum;
Scanner kb = new Scanner(System.in);
System.out.printf("\nEnter a part number (E to end): ");
String pnum = kb.next();
while (!pnum.equalsIgnoreCase("E")) {
int n = search(pnum, index, numRecords);
if (n > 0) {
fp.seek(PartRecordSize * (index[n].recNum - 1));
readPartFromFile(fp).printPart();
}
else System.out.printf("Part not found\n");
System.out.printf("\nEnter a part number (E to end): ");
pnum = kb.next();
} //end while
fp.close();
} //end main
public static Index[] retrieveIndex() throws IOException {
RandomAccessFile f = new RandomAccessFile("index.bin", "rw");
int MaxRecords = f.readInt();
Index[] index = new Index[MaxRecords + 1];
for (int j = 0; j <= MaxRecords; j++) {
String pnum = "";
for (int i = 0; i < PartNumSize; i++) pnum += f.readChar();
index[j] = new Index(pnum, f.readInt());
}
f.close();
return index;
} //end retrieveIndex
public static Part readPartFromFile(RandomAccessFile f) throws IOException {
String pname = "";
for (int h = 0; h < PartNumSize; h++) pname += f.readChar();
char[] name = new char[StringFixedLength];
for (int h = 0; h < StringFixedLength; h++) name[h] = f.readChar();
String hold = new String(name, 0, StringFixedLength);
return new Part(pname, hold.trim(), f.readInt(), f.readDouble());
} //end readPartFromFile
public static int search(String key, Index[] list, int n) {
//searches list[1..n] for key. If found, it returns the location; otherwise
//it returns the negative of the location in which key should be inserted.
int lo = 1, hi = n;
while (lo <= hi) { // as long as more elements remain to consider
int mid = (lo + hi) / 2;
int cmp = key.compareToIgnoreCase(list[mid].partNum);
if (cmp == 0) return mid; // search succeeds
if (cmp < 0) hi = mid - 1; // key is 'less than' list[mid].partNum
else lo = mid + 1; // key is 'greater than' list[mid].partNum
}