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java IO
Hi,
this is also continuation of my previous question.
following code in Bold is working fine but it resets my entered info each time I do Debug or Run. I what my data not to be overwritten each time.
import java.io.*;
import java.util.*;
public class Gramata3 {
public static void main(String[] args) {
String[][] books = {
// book author year
{ "Head First Java", "Bates and Sierra", "2003" },
{ "Thinking In Java", "Bruce Eckel", "2002" },
{ "Learning Java", "Niemeyer and Knudsen", "2000" },
{ "Developing Java Sortware", "Winder and Roberts", "2000" }
};
File file = new File("gramata3.txt");
try {
PrintWriter out = new PrintWriter(
new FileWriter(file));
for(int j = 0; j < books.length; j++) {
out.println(books[j][2] + " " + books[j][0] + " by " + books[j][1]);
}
out.close();
} catch(IOException e) {
System.out.println("write error: " + e.getMessage());
}
BufferedReader reader = new BufferedReader(
new InputStreamReader(System.in));
try {
System.out.println("Enter a book, see book list " +
"or quit? 'e'/'s'/'q'");
String choice = reader.readLine();
while(!choice.equalsIgnoreCase("q")) {
if(choice.equals("e")) {
System.out.print("Enter name of the book: ");
String book = reader.readLine();
System.out.println("enter author");
String author = reader.readLine();
System.out.println("enter year");
String year = reader.readLine();
PrintWriter out = new PrintWriter(
new FileWriter(file, true));
out.println(year + " " + book + " by " + author);
out.close();
} else if(choice.equals("s")) {
System.out.println("sort books by title, author " +
"or date? 't'/'a'/'d'");
choice = reader.readLine().toLowerCase();
int index = choice.equals("t") ? 1 :
choice.equals("a") ? 2 : 0;
showBooks(file, index);
}
System.out.println("Enter a book see, book list " +
"or quit? 'e'/'s'/'q'");
choice = reader.readLine();
}
reader.close();
} catch(IOException e) {
System.out.println("main I/O error: " + e.getMessage());
}
}
private static void showBooks(File file, int index) {
List<String> list = new ArrayList<String>();
try {
BufferedReader in = new BufferedReader(
new FileReader(file));
String line;
while((line = in.readLine()) != null) {
list.add(line);
}
in.close();
} catch(IOException e) {
System.out.println("showBooks I/O error: " + e.getMessage());
}
sort(list, index);
}
private static void sort(List<String> list, int index) {
// Parse the lines into the title, author and date data.
String[][] data = new String[list.size()][];
for(int j = 0; j < list.size(); j++) {
String book = (String)list.get(j);
data[j] = getBookData(book);
}
// Sort the books.
for(int j = 0; j < data.length; j++) {
String min = data[j][index];
int minIndex = j;
for(int k = j+1; k < data.length; k++) {
int compare = 0;
switch(index) {
case 0: // year
Integer n = Integer.valueOf(min);
compare = Integer.valueOf(data[k][index]).compareTo(n);
break;
case 1: // title
String s = String.valueOf(min);
compare = data[k][index].compareTo(s);
break;
case 2: // author
String name = getComparableName(data[k][index]);
s = getComparableName(min);
compare = name.compareTo(s);
}
if(compare < 0) {
min = data[k][index];
minIndex = k;
}
}
if(minIndex != j) {
// Found lower sort value, swap book elements.
String[] temp = data[j];
data[j] = data[minIndex];
data[minIndex] = temp;
}
}
// Print the sorted array.
for(int j = 0; j < data.length; j++) {
String year = data[j][0];
String title = data[j][1];
String author = data[j][2];
System.out.println(year + " " + title + " by " + author);
}
System.out.println("------------------");
}
private static String[] getBookData(String book) {
String[] data = new String[3];
int start = book.indexOf(" ");
data[0] = book.substring(0, start); // year
int by = book.indexOf(" by ", start+1);
data[1] = book.substring(start, by); // title
data[2] = book.substring(by + 4); // author
return data;
}
private static String getComparableName(String s) {
boolean hasAnd = s.indexOf(" and ") != -1;
int last = s.lastIndexOf(" ");
if(!hasAnd && last != -1) {
// Put last name first for accurate sorting.
s = s.substring(last+1) + " " + s.substring(0, last);
}
return s;
}
}
dmacvittie suggested to comment following lines but then programm is not working:
{ "Head First Java", "Bates and Sierra", "2003" },
{ "Thinking In Java", "Bruce Eckel", "2002" },
{ "Learning Java", "Niemeyer and Knudsen", "2000" },
{ "Developing Java Sortware", "Winder and Roberts", "2000" }
};
File file = new File("gramata3.txt");
try {
PrintWriter out = new PrintWriter(
new FileWriter(file));
for(int j = 0; j < books.length; j++) {
out.println(books[j][2] + " " + books[j][0] + " by " + books[j][1]);
}
out.close();
} catch(IOException e) {
System.out.println("write error: " + e.getMessage());
}
Can someone help me please. Thanks!
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Linear Mode
