comparing the file before i append it to the other

[Tom Breuer]

I have two files that need to be made into one file. The thing is file 1 has records A,B,C,D E and File 2 has records C,D,E,F,G,H. So now my program writes the final record as A,B,C,D,E,C,D,E,F,G,H.(some duplicate records) How can I get the file to just write the built file as ABCDEFGH.(each record is a line long) here is the program so far but I am confused about the compare part. any help would be great
import java.io.*;
import java.util.*;
public class MergeFile {
public static void main(String[] args) throws Exception {
File f1 = new File("C:\\Downloaded\\File.001");
File f2 = new File("C:\\Downloaded\\File.002");
File outFile = new File("C:\\Downloaded\\builtfile.001");
FileWriter outFlWr= new FileWriter(outFile);
BufferedWriter bufOutput = new BufferedWriter(outFlWr);
if(f1.exists() && f2.exists()) {
System.out.println("yes there are two files");
try {
FileReader inFlRd = new FileReader(f1);
BufferedReader bufInput = new BufferedReader(inFlRd);
String line;
line = bufInput.readLine();
while (line != null) {
bufOutput.write(line, 0, line.length());
bufOutput.newLine();
line = bufInput.readLine();
}//end while
bufInput.close();
}//end try
catch (IOException e) {
e.printStackTrace();
}
try {
FileReader inFlRd2 = new FileReader(f2);
BufferedReader bufInput = new BufferedReader(inFlRd2);
String line;
line = bufInput.readLine();
while (line != null) {
bufOutput.write(line, 0, line.length());
bufOutput.newLine();
line = bufInput.readLine();
}//end while
bufInput.close();
bufOutput.close();
}//end try
catch (IOException e) {
e.printStackTrace();
}
}//end if
else {
System.out.println("Process ran ran normal, only one PunchFile exists");
}
}//end main
}//end class

[This message has been edited by Tom Breuer (edited June 21, 2001).]

[Ryan Langley]

Hello,
How do you distinguish the records? Is there a primary key or a unigue field in the record that you can use for comparisons? If so, I would read all the keys and make two separate lists of them. I would then discard the duplicate keys from the list that is from the file that is going to be appended, and then read through that file and append the records with those keys. This won't be too tough to do if you use RandomAccessFile. Hope this helps!
Cheers,
RL

[jake mullet]

Im sorry Im not experienced enough to understand, but I've never used RandomaccessFile. Do you know where there are any examples for what I need it for? thanks

[Ryan Langley]

Hello,
RandomAccessFile allows you to seek to a position in a file, say 5 characters/bytes after a newline character ('\n'). And then read x characters/bytes from that position. You could then seek to a different part of the same file, say 5 characters/bytes after the next newline character, and read some more characters/bytes. Unlike the other Readers/InputStreams it is not sequential access to a file, but random access to a file. You can access any part of the file at any time, as opposed starting from the beginning of the file and having to read characters/bytes to get to the part of the file you really want to read. Look it up in the javadocs. Here's a quick example that will read the 5th character of everyline and print it to screen:

import java.io.*;
public class FifthCharRandomAccess {
  public static void main(String[] args) throws IOException {
    File textFile = new File("text.txt");
FileWriter fw = new FileWriter(textFile);
PrintWriter pw = new PrintWriter(fw);

StringBuffer sb = new StringBuffer();
sb.append("\"Seldom we find,\" says Solomon Don Dunce,\n");
sb.append("\"Half an idea in the profoundest sonnet.\n");
sb.append("Through all the flimsy things we see at once\n");
sb.append("As easily as through a Naples bonnet-\n");
sb.append("Trash of all trash!- how can a lady don it?\n");
sb.append("Yet heavier far than your Petrarchan stuff-\n");
sb.append("Owl-downy nonsense that the faintest puff\n");
sb.append("Twirls into trunk-paper the while you con it.\"\n");
sb.append("And, veritably, Sol is right enough.\n");
sb.append("The general tuckermanities are arrant\n");
sb.append("Bubbles- ephemeral and so transparent-\n");
sb.append("But this is, now- you may depend upon it-\n");
sb.append("Stable, opaque, immortal- all by dint\n");
sb.append("Of the dear names that he concealed within 't.");

pw.print(sb.toString());
pw.close();
fw.close();

RandomAccessFile raf = new RandomAccessFile(textFile, "r");
long pos = 0;
while(pos < raf.length()) {
          pos += 4;
  raf.seek(pos);
  System.out.print((char)raf.read());
  while(pos != raf.length() && (char)raf.read() != '\n') {
    raf.seek(++pos);
  }
  ++pos;
}
raf.close();
  }
}

------------------
Cheers,
RL
[This message has been edited by Ryan Langley (edited June 25, 2001).]

[Paul Michael]

hey Tom! you really don't have to use RandomAccessFile if you're already comfortable with what you originally did. you just have to tell us the contents of each record so we can devise something that checks for duplicates. if you'll just going to be dealing with String Objects then that wouldn't be so hard...
[This message has been edited by Paul Michael Laborte (edited July 07, 2001).]