I'm doing a Phone Directory project and we have to read from a directory file telnos.txt
I'm using a Scanner to load the data from the file telnos.txt, using a loadData method from a previous question I asked here on StackOverflow.
I noticed attempts to find a user always returned Not Found, so I added a few System.out.printlns in the methods to help me see what was going on. It looks like the scanner isn't reading anything from the file. Weirdly, it is printing the name of the file as what should be the first line read, which makes me think I've missed something very very simple here.
Console
run:
telnos.txt
null
loadData tested successfully
Please enter a name to look up: John
-1
Not found
BUILD SUCCESSFUL (total time: 6 seconds)
ArrayPhoneDirectory.java
import java.util.*;
import java.io.*;
public class ArrayPhoneDirectory implements PhoneDirectory {
private static final int INIT_CAPACITY = 100;
private int capacity = INIT_CAPACITY;
// holds telno of directory entries
private int size = 0;
// Array to contain directory entries
private DirectoryEntry[] theDirectory = new DirectoryEntry[capacity];
// Holds name of data file
private final String sourceName = "telnos.txt";
File telnos = new File(sourceName);
// Flag to indicate whether directory was modified since it was last loaded or saved
private boolean modified = false;
// add method stubs as specified in interface to compile
public void loadData(String sourceName) {
Scanner read = new Scanner("telnos.txt").useDelimiter("\\Z");
int i = 1;
String name = null;
String telno = null;
while (read.hasNextLine()) {
if (i % 2 != 0)
name = read.nextLine();
else
telno = read.nextLine();
add(name, telno);
i++;
}
}
public String lookUpEntry(String name) {
int i = find(name);
String a = null;
if (i >= 0) {
a = name + (" is at position " + i + " in the directory");
} else {
a = ("Not found");
}
return a;
}
public String addChangeEntry(String name, String telno) {
for (DirectoryEntry i : theDirectory) {
if (i.getName().equals(name)) {
i.setNumber(telno);
} else {
add(name, telno);
}
}
return null;
}
public String removeEntry(String name) {
for (DirectoryEntry i : theDirectory) {
if (i.getName().equals(name)) {
i.setName(null);
i.setNumber(null);
}
}
return null;
}
public void save() {
PrintWriter writer = null;
// writer = new PrintWriter(FileWriter(sourceName));
}
public String format() {
String a;
a = null;
for (DirectoryEntry i : theDirectory) {
String b;
b = i.getName() + "/n";
String c;
c = i.getNumber() + "/n";
a = a + b + c;
}
return a;
}
// add private methods
// Adds a new entry with the given name and telno to the array of
// directory entries
private void add(String name, String telno) {
System.out.println(name);
System.out.println(telno);
theDirectory[size] = new DirectoryEntry(name, telno);
size = size + 1;
}
// Searches the array of directory entries for a specific name
private int find(String name) {
int result = -1;
for (int count = 0; count < size; count++) {
if (theDirectory[count].getName().equals(name)) {
result = count;
}
System.out.println(result);
}
return result;
}
// Creates a new array of directory entries with twice the capacity
// of the previous one
private void reallocate() {
capacity = capacity * 2;
DirectoryEntry[] newDirectory = new DirectoryEntry[capacity];
System.arraycopy(theDirectory, 0, newDirectory,
0, theDirectory.length);
theDirectory = newDirectory;
}
}
ArrayPhoneDirectoryTester.java
import java.util.Scanner;
public class ArrayPhoneDirectoryTester {
public static void main(String[] args) {
//create a new ArrayPhoneDirectory
PhoneDirectory newTest = new ArrayPhoneDirectory();
newTest.loadData("telnos.txt");
System.out.println("loadData tested successfully");
System.out.print("Please enter a name to look up: ");
Scanner in = new Scanner(System.in);
String name = in.next();
String entryNo = newTest.lookUpEntry(name);
System.out.println(entryNo);
}
}
telnos.txt
John
123
Bill
23
Hello
23455
Frank
12345
Dkddd
31231
In your code:
Scanner read = new Scanner("telnos.txt");
Is not going to load file 'telnos.txt'. It is instead going to create a Scanner object that scans the String "telnos.txt".
To make the Scanner understand that it has to scan a file you have to either:
Scanner read = new Scanner(new File("telnos.txt"));
or create a File object and pass its path to the Scanner constructor.
In case you are getting "File not found" errors you need to check the current working directory. You could run the following lines and see if you are indeed in the right directory in which the file is:
String workingDir = System.getProperty("user.dir");
System.out.println("Current working directory : " + workingDir);
You need to also catch the FileNotFoundException in the function as follows:
public void loadData(String sourceName) {
try {
Scanner read = new Scanner(new File("telnos.txt")).useDelimiter("\\Z");
int i = 1;
String name = null;
String telno = null;
while (read.hasNextLine()) {
if (i % 2 != 0)
name = read.nextLine();
else {
telno = read.nextLine();
add(name, telno);
}
i++;
}
}catch(FileNotFoundException ex) {
System.out.println("File not found:"+ex.getMessage);
}
}
You are actually parsing the filename not the actual file contents.
Instead of:
new Scanner("telnos.txt")
you need
new Scanner( new File( "telnos.txt" ) )
http://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html
Related
The program is giving correct output when System.out.println(mem[i].memName); but the array of class "member" is giving output (alex alex alex alex) i.e of the last line of the file (mentioned at the END of the CODE)
it should give all the names listed in the file.
import java.io.*;
import java.util.*;
class member//CLASS TO BE USED AS ARRAY TO STORE THE PRE REGISTERED MEMBERS FED INSIDE
{ //THE FILE "member.txt"
static int memId;
static String memName, memEmail, memPh, date;
}
public class entry// file name
{
static DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy/MM/dd");
static LocalDateTime now = LocalDateTime.now();
static Scanner input = new Scanner(System.in);
static member[] mem = new member[100];
static trainer[] tr = new trainer[100];
static FileWriter fwriter = null;
static BufferedWriter bwriter = null;
static FileReader fread = null;
static BufferedReader bread = null;
static void memberEntry() {
int i = 0;
System.out.println("NEW MEMBER IS BEING ADDED");
try {
fwriter = new FileWriter("C:\\Users\\itisa\\OneDrive\\Desktop\\GYM
PROJECT\\member.txt
",true);
bwriter = new BufferedWriter(fwriter);
System.out.println("Member ID is being automatically genrated");
int autoID = 101 + getMemberRecords();//Fetching the number of members so that ID can
//Be genrated automatically
i = autoID % 100;//jumping toward the next loaction location
System.out.println("Member ID of new member is" + autoID);
mem[i].memId = autoID;
System.out.print("Enter the name of the member:");
mem[i].memName = input.next();
System.out.print("Enter the email address of memeber:");
mem[i].memEmail = input.next();
System.out.print("Enter the contact number of memeber:");
mem[i].memPh = input.next();
System.out.println("Date has been feeded automatically:" + dtf.format(now));
mem[i].date = dtf.format(now);
bwriter.write(String.valueOf(mem[i].memId));
bwriter.write("|");
bwriter.write(mem[i].memName);
bwriter.write("|");
bwriter.write(mem[i].memEmail);
bwriter.write("|");
bwriter.write(mem[i].memPh);
bwriter.write("|");
bwriter.write(mem[i].date);
bwriter.write("\n");
System.out.println("MEMBER CREATED SUCCESSFULLY");
System.out.println("---------------------------------------");
bwriter.close();
} catch (IOException e) {
System.out.print(e);
}
}
static int getMemberRecords() {
int count = 0, i = 0;
try {
fread = new FileReader("C:\\Users\\itisa\\OneDrive\\Desktop\\GYM PROJECT\\member.txt");
bread = new BufferedReader(fread);
String lineRead = null;
while ((lineRead = bread.readLine()) != null)//Just to get to know the number of member
//alreadyinside the file
{
String[] t = lineRead.split("\\|");
mem[i].memId = Integer.parseInt(t[0]);
mem[i].memName = t[1];
mem[i].memEmail = t[2];
mem[i].memPh = t[3];
mem[i].date = t[4];
i++;
count++;
}
System.out.println(mem[0].memName);//should print the 1st name present in the name
//i.e, RAVI
} catch (IOException e) {
System.out.println(e);
}
return count;
}
public static void main(String[] args) throws IOException {
System.out.println("Total number of accounts:" + getMemberRecords());
}
}
Elements stored in the file:
101|RAVI|itisadi23#gmai.com|9102019656|2020/04/30
102|aditya|adi#gmail.com|9386977983|2020/04/30
103|anurag|anu#ymail.com|10000000000|2020/04/30
104|alex|alex123#mail.com|2829578303|2020/04/30
Expected output:
RAVI
Total number of accounts = 4
My output:
alex
Total number of accounts=4
In Short it is giving last name as output no matter what index number is given to fetch the data.
Your member class members must not be static, if they are, they're shared by every member class object.
The other problem is that your member array nodes are not being initialized, you'll need:
Live demo
class member
{
int memId; //non-static
String memName, memEmail, memPh, date; //non-static
}
and
//...
while ((lineRead = bread.readLine()) != null) {
String[] t = lineRead.split("\\|");
mem[i] = new member(); // initialize every node
mem[i].memId = Integer.parseInt(t[0]);
mem[i].memName = t[1];
mem[i].memEmail = t[2];
mem[i].memPh = t[3];
mem[i].date = t[4];
i++;
count++;
}
System.out.println(mem[0].memName);
//...
Output:
RAVI
Note that you can use ArrayList or other java collection.
There are plenty of problems as I am new, I can find spelling and such, but I can't seem to call some of the methods, and referencing some objects also doesn't seem to work. I know it's a lot of code, but this is one puzzle I can't seem to solve, and my grade depends on this. My teacher has no free to help as he is working on a coding project of his own. Please Help me!
import java.io.*;
import java.util.Scanner;
public class FlatFileDatabase{
private final String PATH="table\\";
public boolean createTable(String file, String columns){
//create table
//allows users to specify what meta-information is in each column.
//check for hashtags.
if(!columns.startsWith("#")){
return false;
}
//check for the minimum amount of columns using String split.
if(columns.split("::").length < 2){
return false;
}
//write columns
PrintWriter pw = new PrintWriter(PATH + file);
pw.println(columns);
pw.close();
//try-catch-finally errors and exit
}
public void destroyTable(String table){
//deletes table
File f = new File(PATH + table);
f.delete();
}
public void create(String record, String file) throws IOException{
//makes method for printwriter
PrintWriter pw = new PrintWriter(new FileWriter(PATH+file,true));
pw.println(record);
pw.close();
}
public String findOne(String key, String table){
//open file
File f = new File(PATH + table);
Scanner sc = new Scanner("table.txt");
//the variables are just placeholders
String rawRecord = null;
String[] splitRecord;
String recordKey;
String record = null;
boolean recordNotFound = true;
//read each line until find record
while(recordNotFound && sc.hasNext()){
rawRecord = sc.nextLine();
splitRecord = rawRecord.split("::");
rawRecord = splitRecord[0];
if(key.equals(recordKey)){
record = recordKey;
recordNotFound = false;
}
}
//return
return record;
}
public boolean update(String key, String record, String table){
//helper variables
String contents = "";
String rawRecord;
String splitRecord[];
String recordKey;
//open
File f = new File(PATH + table);
Scanner sc = new Scanner(f);
//search for record
while(sc.hasNext()){
rawRecord = sc.nextLine();
splitRecord = rawRecord.split("::");
rawRecord = splitRecord[0];
if(key.equals(recordKey)){
contents += record;
} else {
contents += rawRecord;
}
}
f.close();
//if found, update record
//make private method of this and finding files
f.create();
//return
}
public boolean destroy(String key, String table){
//update
//return update(" ");
}
public static void main(String[]args){
createTable ct = new createTable();
destroyTable dt = new destroyTable();
findOne fo = new findOne();
update upd = new update();
Scanner sc = new Scanner(System.in);
System.out.print("What would you like to do?/n/n1]create a table/n2]delete table/n3]opentable/n4]update table");
int a = sc.nextInt();
if(a==1){
createTable();
}else if(a==2){
destroyTable();
}else if(a==3){
findOne();
}else{
update();
}
}
}
I am trying to do a file I/O in eclipse. Here is the code:
import java.io.FileInputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.StringTokenizer;
public class TextDB {
public static final String SEPARATOR = "|";
// an example of reading
public static ArrayList readProfessors(String filename) throws IOException {
// read String from text file
ArrayList stringArray = (ArrayList) read(filename);
ArrayList alr = new ArrayList();// to store Professors data
for (int i = 0; i < stringArray.size(); i++) {
String st = (String) stringArray.get(i);
// get individual 'fields' of the string separated by SEPARATOR
StringTokenizer star = new StringTokenizer(st, SEPARATOR); // pass in the string to the string tokenizer using delimiter ","
String name = star.nextToken().trim(); // first token
String email = star.nextToken().trim(); // second token
int contact = Integer.parseInt(star.nextToken().trim()); // third token
// create Professor object from file data
Professor prof = new Professor(name, email, contact);
// add to Professors list
alr.add(prof);
}
return alr;
}
// an example of saving
public static void saveProfessors(String filename, List al) throws IOException {
List alw = new ArrayList();// to store Professors data
for (int i = 0; i < al.size(); i++) {
Professor prof = (Professor) al.get(i);
StringBuilder st = new StringBuilder();
st.append(prof.getName().trim());
st.append(SEPARATOR);
st.append(prof.getEmail().trim());
st.append(SEPARATOR);
st.append(prof.getContact());
alw.add(st.toString());
}
write(filename, alw);
}
/**
* Write fixed content to the given file.
*/
public static void write(String fileName, List data) throws IOException {
PrintWriter out = new PrintWriter(new FileWriter(fileName));
try {
for (int i = 0; i < data.size(); i++) {
out.println((String) data.get(i));
}
} finally {
out.close();
}
}
/**
* Read the contents of the given file.
*/
public static List read(String fileName) throws IOException {
List data = new ArrayList();
Scanner scanner = new Scanner(new FileInputStream(fileName));
try {
while (scanner.hasNextLine()) {
data.add(scanner.nextLine());
}
} finally {
scanner.close();
}
return data;
}
public static void main(String[] aArgs) {
TextDB txtDB = new TextDB();
String filename = "professor.txt";
try {
// read file containing Professor records.
ArrayList al = TextDB.readProfessors(filename);
for (int i = 0; i < al.size(); i++) {
Professor prof = (Professor) al.get(i);
System.out.println("Name " + prof.getName());
System.out.println("Contact " + prof.getContact());
}
Professor p1 = new Professor("Joseph", "jos#ntu.edu.sg", 67909999);
// al is an array list containing Professor objs
al.add(p1);
// write Professor record/s to file.
TextDB.saveProfessors(filename, al);
} catch (IOException e) {
System.out.println("IOException > " + e.getMessage());
}
}
}
And my Professor class:
import java.io.Serializable;
public class Professor implements Serializable {
private String name;
private String email;
private int contact;
public Professor(String n, String e, int c) {
name = n;
email = e;
contact = c;
}
public String getName() {
return name;
}
public int getContact() {
return contact;
}
public String getEmail() {
return email;
}
public boolean equals(Object o) {
if (o instanceof Professor) {
Professor p = (Professor) o;
return (getName().equals(p.getName()));
}
return false;
}
}
However, when I run it, the compiler told the the specified file "professor.txt" is not found. I thought the compiler will create the text file automatically based on these code?
Thanks in advance.
Before attempting to read the file in your application, create it if it doesn't exist, either directly :
String filename = "professor.txt" ;
File file = new File(fileName);
if(!file.exists()){
file.createNewFile();
}
Or by calling your write method.
String filename = "professor.txt" ;
File file = new File(fileName);
if(!file.exists()){
TextDB.saveProfessors(filename, new ArrayList());
}
The PrintWriter will create the file for you, even though nothing is written to it (like with this empty list).
In your main you are firstly reading the file and then write it: if the file doesn't exist it will throw you the exception. Probably, the first time you ran it, the file was present (maybe you have write the code to write the file first and then you have launch it).
so, two solutions...
First: change the order of your main.
public static void main(String[] aArgs) {
TextDB txtDB = new TextDB();
String filename = "professor.txt";
try {
Professor p1 = new Professor("Joseph", "jos#ntu.edu.sg", 67909999);
// al is an array list containing Professor objs
al.add(p1);
// write Professor record/s to file.
TextDB.saveProfessors(filename, al);
// read file containing Professor records.
ArrayList al = TextDB.readProfessors(filename);
for (int i = 0; i < al.size(); i++) {
Professor prof = (Professor) al.get(i);
System.out.println("Name " + prof.getName());
System.out.println("Contact " + prof.getContact());
}
} catch (IOException e) {
System.out.println("IOException > " + e.getMessage());
}
}
Second: check if the file exist or not and then skip the read of it if it doesn't
public static void main(String[] aArgs) {
TextDB txtDB = new TextDB();
String filename = "professor.txt";
try {
//check if the file exist
File oFile = new File(filename);
if(oFile.exist()) {
// read file containing Professor records.
ArrayList al = TextDB.readProfessors(filename);
for (int i = 0; i < al.size(); i++) {
Professor prof = (Professor) al.get(i);
System.out.println("Name " + prof.getName());
System.out.println("Contact " + prof.getContact());
}
}
Professor p1 = new Professor("Joseph", "jos#ntu.edu.sg", 67909999);
// al is an array list containing Professor objs
al.add(p1);
// write Professor record/s to file.
TextDB.saveProfessors(filename, al);
} catch (IOException e) {
System.out.println("IOException > " + e.getMessage());
}
}
UPDATE after comment:
public static void main(String[] aArgs) {
TextDB txtDB = new TextDB();
String filename = "professor.txt";
try {
//check if the file exist
File oFile = new File(filename);
if(!oFile.exist()) {
oFile.mkdirs(); //optional
oFile.createNewFile();
}
// read file containing Professor records.
ArrayList al = TextDB.readProfessors(filename);
for (int i = 0; i < al.size(); i++) {
Professor prof = (Professor) al.get(i);
System.out.println("Name " + prof.getName());
System.out.println("Contact " + prof.getContact());
}
Professor p1 = new Professor("Joseph", "jos#ntu.edu.sg", 67909999);
// al is an array list containing Professor objs
al.add(p1);
// write Professor record/s to file.
TextDB.saveProfessors(filename, al);
} catch (IOException e) {
System.out.println("IOException > " + e.getMessage());
}
}
So I have a file that has names along with 11 popularity ranks which looks like this. <--- (this is a link) I am a bit confused on what I am suppose to do with this next part that I have for my assignment. Generally I have a name app that looks like this:
public class Name{
private String givenName;
private int[] ranks = new int[11];
public Name(String name, int[] popularityRanks){
givenName = name;
for (int i = 0; i < 11; i++){
ranks[i] = popularityRanks[i];
}
}
public String getName(){
return givenName;
}
public int getPop(int decade){
if (decade >= 1 && decade <= 11){
return ranks[decade];
}
else{
return -1;
}
}
public String getHistoLine(int decade){
String histoLine = ranks[decade] + ": ";
return histoLine;
}
public String getHistogram(){
String histogram = "";
for (int i = 0; i < 11; i++){
histogram += ranks[i] + ": " + this.getHistoLine(i)
+ "\n";
}
return histogram;
}
}
It is not finished for the getHistoLine but that doesn't have anything to do with what I am trying to do. Generally I want to take these names in from the file and create an array of list.
How he describes it:
Create the array in main, pass it to the readNamesFile method and let that method fill it with Name objects
Test this, by printing out various names and their popularity rankings
For example, if main named the array, list, then upon return from the readNamesFile method do something like:
System.out.println( list[0].getName() + list[0].getPop(1) );
This is what my main looks like:
import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;
public class NameApp{
public static void main(String[] args){
Name list[] = new Name()
}
private static void loadFile(){
Scanner inputStream = null;
String fileName = "names.txt";
try {
inputStream = new Scanner (new File(fileName));
}
catch (FileNotFoundException e){
System.out.println("Error opening file named: " + fileName);
System.out.println("Exiting...");
}
while (inputStream.hasNext()){
}
}
}
I am just a bit confused how I can take the name have it send to the Name object list[] and then take the popularity ranks and send it to the Name object list[]. So when I call
list[0].getName()
it will just call the name for one of the lines... Sorry I am a bit new to the java language. Thanks in advance
You need to create a Name list correctly. I would use a List since you don't know how many names there will be;
public static void main(String[] args){
List<Name> list = new ArrayList<Name>();
loadFile();
System.out.println(list.get(0).getPop());
}
private static void loadFile(){
Scanner inputStream = null;
String fileName = "names.txt";
try {
inputStream = new Scanner (new File(fileName));
}
catch (FileNotFoundException e){
System.out.println("Error opening file named: " + fileName);
System.out.println("Exiting...");
}
while (inputStream.hasNext()){
// givenName = something
// ranks = something;
list.add(new Name(givenName, ranks);
}
}
Assuming each line is something like this (from your deleted comment)
A 1 234 22 43 543 32 344 32 43
Your while loop can be something like this
while (inputStream.hasNextLIne()){
String line = inputStream.nextLine();
String tokens = line.split("\\s+");
String givenName = tokens[0];
int[] numList = new int[tokens.lenth - 1];
for (int i = 1; i < tokens.length; i++){
numList[i - 1] = Integer.parseInt(tokens[i].trim());
}
list.add(new Name(givenName, numList);
}
I have 2 files where 1(OrderCatalogue.java) reads in contents of a external file and 2(below). But I'm having the "FileNotFoundException must be caught or declard to be thrown" error for this line "OrderCatalogue catalogue= new OrderCatalogue();" and I understand that because its not in a method. But if i try puting it in a method, the code under the "getCodeIndex" and "checkOut" methods can't work with the error message of "package catalogue does not exist". Anyone has any idea how i can edit my code to make them work? Thank you!!
public class Shopping {
OrderCatalogue catalogue= new OrderCatalogue();
ArrayList<Integer> orderqty = new ArrayList<>(); //Create array to store user's input of quantity
ArrayList<String> ordercode = new ArrayList<>(); //Create array to store user's input of order number
public int getCodeIndex(String code)
{
int index = -1;
for (int i =0;i<catalogue.productList.size();i++)
{
if(catalogue.productList.get(i).code.equals(code))
{
index = i;
break;
}
}
return index;
}
public void checkout()
{
DecimalFormat df = new DecimalFormat("0.00");
System.out.println("Your order:");
for(int j=0;j<ordercode.size();j++)
{
String orderc = ordercode.get(j);
for (int i =0;i<catalogue.productList.size();i++)
{
if(catalogue.productList.get(i).code.equals(orderc))
{
System.out.print(orderqty.get(j)+" ");
System.out.print(catalogue.productList.get(i).desc);
System.out.print(" # $"+df.format(catalogue.productList.get(i).price));
}
}
}
}
And this is my OrderCatalogue file
public OrderCatalogue() throws FileNotFoundException
{
//Open the file "Catalog.txt"
FileReader fr = new FileReader("Catalog.txt");
Scanner file = new Scanner(fr);
while(file.hasNextLine())
{
//Read in the product details in the file
String data = file.nextLine();
String[] result = data.split("\\, ");
String code = result[0];
String desc = result[1];
String price = result[2];
String unit = result[3];
//Store the product details in a vector
Product a = new Product(desc, code, price, unit);
productList.add(a);
}
It seems the OrderCatalogue constructor throws FileNotFoundException. You can initialize catalogue inside Shopping constructor and catch the exception or declare it to throw FileNotFoundException.
public Shopping() throws FileNotFoundException
{
this.catalogue= new OrderCatalogue();
or
public Shopping()
{
try{
this.catalogue= new OrderCatalogue();
}catch(FileNotFoundException e)
blah blah
}