File Read and Write

package kuchana.partha;
 
/*
 Software Architecture Design Patterns in Java
 by Partha Kuchana 
 
 Auerbach Publications
 
 */
 
import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Vector;
 
public class FileUtil {
 
    DataOutputStream dos;
 
    /*
     * Utility method to write a given text to a file
     */
    public boolean writeToFile(String fileName, String dataLine,
	    boolean isAppendMode, boolean isNewLine) {
	if (isNewLine) {
	    dataLine = "\n" + dataLine;
	}
 
	try {
	    File outFile = new File(fileName);
	    if (isAppendMode) {
		dos = new DataOutputStream(new FileOutputStream(fileName, true));
	    } else {
		dos = new DataOutputStream(new FileOutputStream(outFile));
	    }
 
	    dos.writeBytes(dataLine);
	    dos.close();
	} catch (FileNotFoundException ex) {
	    return (false);
	} catch (IOException ex) {
	    return (false);
	}
	return (true);
 
    }
 
    /*
     * Reads data from a given file
     */
    public String readFromFile(String fileName) {
	String DataLine = "";
	try {
	    File inFile = new File(fileName);
	    BufferedReader br = new BufferedReader(new InputStreamReader(
		    new FileInputStream(inFile)));
 
	    DataLine = br.readLine();
	    br.close();
	} catch (FileNotFoundException ex) {
	    return (null);
	} catch (IOException ex) {
	    return (null);
	}
	return (DataLine);
 
    }
 
    public boolean isFileExists(String fileName) {
	File file = new File(fileName);
	return file.exists();
    }
 
    public boolean deleteFile(String fileName) {
	File file = new File(fileName);
	return file.delete();
    }
 
    /*
     * Reads data from a given file into a Vector
     */
 
    public Vector fileToVector(String fileName) {
	Vector v = new Vector();
	String inputLine;
	try {
	    File inFile = new File(fileName);
	    BufferedReader br = new BufferedReader(new InputStreamReader(
		    new FileInputStream(inFile)));
 
	    while ((inputLine = br.readLine()) != null) {
		v.addElement(inputLine.trim());
	    }
	    br.close();
	} // Try
	catch (FileNotFoundException ex) {
	    //
	} catch (IOException ex) {
	    //
	}
	return (v);
    }
 
    /*
     * Writes data from an input vector to a given file
     */
 
    public void vectorToFile(Vector v, String fileName) {
	for (int i = 0; i < v.size(); i++) {
	    writeToFile(fileName, (String) v.elementAt(i), true, true);
	}
    }
 
    /*
     * Copies unique rows from a source file to a destination file
     */
 
    public void copyUniqueElements(String sourceFile, String resultFile) {
	Vector v = fileToVector(sourceFile);
	v = MiscUtil.removeDuplicates(v);
	vectorToFile(v, resultFile);
    }
 
} // end FileUtil
 
class MiscUtil {
 
    public static boolean hasDuplicates(Vector v) {
	int i = 0;
	int j = 0;
	boolean duplicates = false;
 
	for (i = 0; i < v.size() - 1; i++) {
	    for (j = (i + 1); j < v.size(); j++) {
		if (v.elementAt(i).toString().equalsIgnoreCase(
			v.elementAt(j).toString())) {
		    duplicates = true;
		}
 
	    }
 
	}
 
	return duplicates;
    }
 
    public static Vector removeDuplicates(Vector s) {
	int i = 0;
	int j = 0;
	boolean duplicates = false;
 
	Vector v = new Vector();
 
	for (i = 0; i < s.size(); i++) {
	    duplicates = false;
	    for (j = (i + 1); j < s.size(); j++) {
		if (s.elementAt(i).toString().equalsIgnoreCase(
			s.elementAt(j).toString())) {
		    duplicates = true;
		}
 
	    }
	    if (duplicates == false) {
		v.addElement(s.elementAt(i).toString().trim());
	    }
 
	}
 
	return v;
    }
 
    public static Vector removeDuplicateDomains(Vector s) {
	int i = 0;
	int j = 0;
	boolean duplicates = false;
	String str1 = "";
	String str2 = "";
 
	Vector v = new Vector();
 
	for (i = 0; i < s.size(); i++) {
	    duplicates = false;
	    for (j = (i + 1); j < s.size(); j++) {
		str1 = "";
		str2 = "";
		str1 = s.elementAt(i).toString().trim();
		str2 = s.elementAt(j).toString().trim();
		if (str1.indexOf('@') > -1) {
		    str1 = str1.substring(str1.indexOf('@'));
		}
		if (str2.indexOf('@') > -1) {
		    str2 = str2.substring(str2.indexOf('@'));
		}
 
		if (str1.equalsIgnoreCase(str2)) {
		    duplicates = true;
		}
 
	    }
	    if (duplicates == false) {
		v.addElement(s.elementAt(i).toString().trim());
	    }
 
	}
 
	return v;
    }
 
    public static boolean areVectorsEqual(Vector a, Vector b) {
	if (a.size() != b.size()) {
	    return false;
	}
 
	int i = 0;
	int vectorSize = a.size();
	boolean identical = true;
 
	for (i = 0; i < vectorSize; i++) {
	    if (!(a.elementAt(i).toString().equalsIgnoreCase(b.elementAt(i)
		    .toString()))) {
		identical = false;
	    }
	}
 
	return identical;
    }
 
    public static Vector removeDuplicates(Vector a, Vector b) {
 
	int i = 0;
	int j = 0;
	boolean present = true;
	Vector v = new Vector();
 
	for (i = 0; i < a.size(); i++) {
	    present = false;
	    for (j = 0; j < b.size(); j++) {
		if (a.elementAt(i).toString().equalsIgnoreCase(
			b.elementAt(j).toString())) {
		    present = true;
		}
	    }
	    if (!(present)) {
		v.addElement(a.elementAt(i));
	    }
	}
 
	return v;
    }
 
}// end of class