A specific writer

Question

I've looked, but I cannot find a writer that lets you write to a specific line of a file. Like:
blabla.write("text",lineNumber);Is there such a writer?

Answer 1

ok :-)
import java.util.*;
import java.io.*;
- read the file using a buffered reader.
File yourFile = new File("...");
byte[] buf = new byte[file.length()];
try {
FileInputStream fis = new FileInputStream(yourFile);
fis.read(buf,0,file.length());
fis.close();
} catch(IOException e) { e.printStackTrace(); }
- localize the CRs (carriage return, symbol that indicates a line change) (you can do that very easily (but not very efficiently) with a StringTokenizer.
String str = new String(buf, "US-ASCII"); // or whatever charset
StringTokenizer stk = new StringTokenizer(str, "\r\n", false);
- Load a java.util.Vector with every "line" (each line now becomes a element in the Vector).
Vector lines = new Vector();
while (stk.hasMoreTokens()) {
lines.add(stk.nextToken());
- You can now add and remove lines by using insert and remove from the Vector.
System.out.println(lines.get(10)); // prints line 10
lines.add("Hi how are you"); // appends a line
lines.insert(10, "Hi how are you"); // adds this line at line 10
- When it is time to save, iterate thru the Vector and concatenate every elements of the Vector into a StringBuffer.
StringBuffer strb = new StringBuffer("");
for (Enumeration e = lines.elements() ; e.hasMoreElements() ;) {
strb.append(e.nextElement());
- Finally overwrite the original file with the new data.
try {
FileOutputStream fos = new FileOutputStream (yourFile, false);
fos.write(strb.toString("US-ASCII")); // or whatever
fos.close();
} catch(IOException e) { e.printStackTrace(); }
Tell me if it's better.
Anthony