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Is there any way to store the elements present in the file to the to the array of the object in java

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.

Java Flat File database full of compiling errors

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();
}
}
}

Specified text file not found for File I/O in Eclipse

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());
}
}

Scanner from file doesn't seem to be reading file

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

BinarySearch on Object Array List in Java

I am trying to perform binary search on an object array list. The user must type in admin number to perform search. Here is my code :
File Controller class to read file from .text file
public class FileController extends StudentApp{
private String fileName;
public FileController() {
String fileName = "student.txt";
}
public FileController(String fileName) {
this.fileName = fileName;
}
public ArrayList<String> readLine() {
ArrayList<String> studentList = new ArrayList<String>();
try {
FileReader fr = new FileReader(fileName);
Scanner sc = new Scanner(fr);
while (sc.hasNextLine()) {
studentList.add(sc.nextLine());
}
fr.close();
} catch (FileNotFoundException exception) {
System.out.println("File " + fileName + " was not found");
} catch (IOException exception) {
System.out.println(exception);
}
return studentList;
}
Student Class with all the setter & getter and compareTo method
public Student(String adminNo, String name, GregorianCalendar birthDate) {
this.adminNo = adminNo;
this.name = name;
this.birthDate = birthDate;
}
public Student(String record) {
Scanner sc = new Scanner(record);
sc.useDelimiter(";");
adminNo = sc.next();
name = sc.next();
birthDate = MyCalendar.convertDate(sc.next());
test1 = sc.nextInt();
test2 = sc.nextInt();
test3 = sc.nextInt();
}
public String toString(){
return (adminNo + " " + name + " " + MyCalendar.formatDate(this.birthDate));
}
public static ArrayList<Student> readStudent(String file) {
FileController fc = new FileController(file);
ArrayList<Student> recs = new ArrayList<Student>();
ArrayList<String> recsReturn = new ArrayList<String>();
recsReturn = fc.readLine();
for (int index = 0; index < recsReturn.size(); index++) {
String input = recsReturn.get(index);
recs.add(new Student(input));
}
return recs;
}
public int compareTo(Student s) {
return Compare(this, s);
}
public int Compare(Student s1, Student s2){
if(s1.getAdminNo().equals(s2.getAdminNo())) {
return 0;
}else{
return 1;
}
}
Executable main method lies here, in StudentSearch Class
public static void main(String [] args){
Scanner sc = new Scanner(System.in);
ArrayList <Student> studentList = new ArrayList <Student> ();
studentList = Student.readStudent("student.txt");
Collections.sort(studentList);
System.out.println("Enter student admin number: ");
String searchAdminNo = sc.next();
int pos = Collections.binarySearch(studentList, new Student(searchAdminNo));
System.out.println(pos);
}
I want to perform search by using the user input admin number. However, here's the error message:
Exception in thread "main" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Unknown Source)
at java.util.Scanner.next(Unknown Source)
at StudentGradeApps.Student.<init>(Student.java:22)
at StudentGradeApps.StudentSearch.main(StudentSearch.java:14)
I think the problem lies at the compareTo method and my binary search. Because when I removed them, my program can get the array list fine. The error only occurs when I try to perform search on my object list. Any help would be appreciated.
Thanks in advance.

As the error message say, the exception is occurring within the Student constructor -
public Student(String record) {
Scanner sc = new Scanner(record);
sc.useDelimiter(";");
adminNo = sc.next();
name = sc.next();
birthDate = MyCalendar.convertDate(sc.next());
test1 = sc.nextInt();
test2 = sc.nextInt();
test3 = sc.nextInt();
}
You are invoking the constructor here -
int pos = Collections.binarySearch(studentList, new Student(searchAdminNo));
searchAdminNo probably doesn't have that many tokens (delimited by ;) as you are reading in the constructor.