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Java set array size of 2D-array after declaration

I have a method that should return a 2D-array which is always structured like this:
int [][] = {{100}, {5}, {1,5,7,8,30,60,...}
My problem is that when I call the method I don't know how long the 3rd array will be. This is my code right now:
public static int[][] readFile(int max, int types, String fileName) {
int [][]result = new int[3][];
try {
FileReader reader = new FileReader(fileName);
BufferedReader bufferedReader = new BufferedReader(reader);
String line;
int currentLine = 0;
while ((line = bufferedReader.readLine()) != null) {
String[] numbers = line.split(" ");
System.out.println(line);
if (currentLine == 0) {
result[0][0] = Integer.parseInt(numbers[0]);
result[1][0] = Integer.parseInt(numbers[1]);
}else if (currentLine == 1) {
int []theSlices = new int[numbers.length];
result[2][0] = theSlices; //-> obviously error
for(int i = 0; i<numbers.length; i++) {
theSlices[i] = Integer.parseInt(numbers[i]);
}
return result;
}
currentLine++;
}
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
;
return null;
}
My code right now is obviously not working but how can I fix it? Happy for every help :)

How return a multidimensional arrayList in java?

I want to create a multidimensional array and pass it as a parameter in a method and then fill the arrayList with elements and return the new version of the arrayList to be able to use that array in different classes but I get java.lang.NoSuchMethodError: I think the problem is about the way i return the array. I searched but I could not find . How can I do it correctly?
here is my code;
public test{
public static List<List<String>> 2Darray=new ArrayList<List<String>>(); // TE ERROR IN THIS LINE
public List<List<String>> fillArray(List<List<String>> array){
BufferedReader in = null;
ArrayList<String> row = new ArrayList<String>();
try {
in = new BufferedReader(new FileReader("sampleFile.txt"));
String read = null;
while ((read = in.readLine()) != null) {
String[] splited = read.split("\\s+");
for(int i=0; i<splited.length ; i++){
row.add(splited[i]);
}
array.add(row);
}
} catch (IOException e) {
System.out.println("There was a problem: " + e);
e.printStackTrace();
} finally {
try {
in.close();
} catch (IOException e) {
}
return array;
}

A little tinkering (just getting it to compile) results in this which seems not to have a problem. Perhaps your issue is elsewhere.
public List<List<String>> fillArray(List<List<String>> array) {
BufferedReader in = null;
ArrayList<String> row = new ArrayList<String>();
try {
in = new BufferedReader(new FileReader("sampleFile.txt"));
String read = null;
while ((read = in.readLine()) != null) {
String[] splited = read.split("\\s+");
for (int i = 0; i < splited.length; i++) {
row.add(splited[i]);
}
array.add(row);
}
} catch (IOException e) {
System.out.println("There was a problem: " + e);
e.printStackTrace();
} finally {
try {
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return array;
}
BTW: You should really use try with resources - it is much clearer.

Modified your code a bit so that it compiled, and replaced the reading from a text file to reading a string. There were several issues, but it seems to work. Give it a try.
The main problems I noticed were mismatching curly braces, and starting a variable name with a number.
import java.util.*;
import java.io.*;
public class Main {
public static List<List<String>> array2D = new ArrayList<List<String>>();
public List<List<String>> fillArray(List<List<String>> array) {
BufferedReader in = null;
ArrayList<String> row = new ArrayList<String>();
try {
String str = "Some test text";
InputStream is = new ByteArrayInputStream(str.getBytes());
//in = new BufferedReader(new FileReader("sampleFile.txt"));
in = new BufferedReader(new InputStreamReader(is));
String read = null;
while ((read = in.readLine()) != null) {
String[] splited = read.split("\\s+");
for(int i=0; i<splited.length ; i++) {
row.add(splited[i]);
}
array.add(row);
}
}
catch (IOException e) {
System.out.println("There was a problem: " + e);
e.printStackTrace();
}
finally {
try {
in.close();
}
catch (IOException e) {
}
}
return array;
}
public static void main(String[] args) {
Main main = new Main();
List<List<String>> test = main.fillArray(array2D);
for(int i = 0; i < test.size(); i++) {
for(int j = 0; j < test.get(i).size(); j++) {
System.out.println(test.get(i).get(j));
}
}
}
}

url.openstream became slow after some loops

Being a beginner in programing I'm actually writing a program to practice, wich use url.open to download pages on a forum but after 88-90 loops the url.openstream became very slow and slow down all the program's execution and i don't know why. i searched on internet the explanations but not found it.
private Set<utilisateur> arbretemp = new HashSet<utilisateur>();
private ArrayList<String> arbretempString = new ArrayList<String>();
private ArrayList<utilisateur> tempArray = new ArrayList<utilisateur>();
private String lienPartie1;
private String lienPartie2;
private int nbrePage;
private String nom;
--
String temporaire = "";
for (int i = 1; i <= nbrePage; i++) {
String line = "";
String lien = lienPartie1 + i + lienPartie2;
bar.setValue(i);
try {
url = new URL(lien);
is = url.openStream();
br = new BufferedReader(new InputStreamReader(is));
System.out.println("avant while");
while (((line = br.readLine()) != null)) {
System.out.println("debut de while");
if (((line.contains("alt=")) && line.contains("class=\"user-avatar-msg\""))) {
line = line.trim();
String[] temp = line.split("\"");
temporaire = temp[5] + " \r";
temp = temporaire.split("\"");
byte[] test = temporaire.getBytes();
if (!(temporaire.equalsIgnoreCase(""))) {
utilisateur utiltemp = new utilisateur(temporaire);
if (arbretemp.add(utiltemp)) {
} else {
arbretempString.add(temporaire);
}
}
}
}
System.out.println("fin de while");
} catch (MalformedURLException mue) {
} catch (IOException ioe) {
ioe.printStackTrace();
} finally {
try {
if (is != null)
is.close();
} catch (IOException ioe) {
// nothing to see here
}
}
String s = "page " + i + "/" + nbrePage;
}
System.out.println("fin de boucle");
Iterator it = arbretemp.iterator();
for (utilisateur a : arbretemp) {
// System.out.println(a.nom);
a.ajouterNbrePost(arbretempString);
}
TreeSet<utilisateur> salComp = new TreeSet<utilisateur>(new utilisateurComp());
salComp.addAll(arbretemp);
tempArray.addAll(arbretemp);
tempArray.sort(new utilisateurComp());
}
as you see it's in french but i hope you will understand anyway.
thanks for your reply and reading

JAVA : file I/O

I have got two text files with data in the following format
data.txt file as following format
A 10
B 20
C 15
data1.txt file is in format (start node,end node, distance):
A B 5
A C 10
B C 20
I am trying to implement a search strategy, for that I need to load the data from data.txt and ONLY the start node and end node from data1.txt (i.e. I dont need the distance). I need to store this information in a stack as I think it would be a best data structure for implementing greedy search.
Actually I am not sure how to get started with file I/O to read these files and store them in array to implement greedy search. So I would highly appreciate any starting idea on how to proceed.
I am new to this, so please bear with me. Any help is much appreciated. Thanks.
EDIT:
Here is what I have got till now
String heuristic_file = "data.txt";
try
{
FileReader inputHeuristic = new FileReader(heuristic_file);
BufferedReader bufferReader = new BufferedReader(inputHeuristic);
String line;
while ((line = bufferReader.readLine()) != null)
{
System.out.println(line);
}
bufferReader.close();
} catch(Exception e) {
System.out.println("Error reading file " + e.getMessage());
}

My approach, doesn't differ fundamentally from the others. Please regard the try/catch/finally blocks. Always put the closing statements into the finally block, so the opened file is guaranteed to be closed, even if an exception was thrown while reading the file.
The part between the two //[...] could surely be done more efficient. Maybe reading the whole file in one take and then parsing the text backwards and searching for a line-break? Maybe a Stream-API supports to set the reading position. I honestly don't know. I didn't need that, up to now.
I chose to use the verbose initialization of the BufferedReader, because then you can specify the expected encoding of the file. In your case it doesn't matter, since your files do not contain symbols out of the standard ASCII range, but I believe it's a semi-best-practice.
Before you ask: r.close() takes care of closing the underlying InputStreamReader and FileInputStream in the right order, till all readers and streams are closed.
public static void readDataFile(String dir, String file1, String file2)
throws IOException
{
File datafile1 = new File(dir, file1);
File datafile2 = new File(dir, file2);
if (datafile1.exists())
{
BufferedReader r = null;
try
{
r = new BufferedReader(
new InputStreamReader(
new FileInputStream(datafile1),
"UTF-8"
)
);
String row;
Stack<Object[]> s = new Stack<Object[]>();
String[] pair;
Integer datapoint;
while((row = r.readLine()) != null)
{
if (row != null && row.trim().length() > 0)
{
// You could use " " instead of "\\s"
// but the latter regular expression
// shorthand-character-class will
// split the row on tab-symbols, too
pair = row.split("\\s");
if (pair != null && pair.length == 2)
{
datapoint = null;
try
{
datapoint = Integer.parseInt(pair[1], 10);
}
catch(NumberFormatException f) { }
// Later you can validate datapairs
// by using
// if (s.pop()[1] != null)
s.add(new Object[] { pair[0], datapoint});
}
}
}
}
catch (UnsupportedEncodingException e1) { }
catch (FileNotFoundException e2) { }
catch (IOException e3) { }
finally
{
if (r != null) r.close();
}
}
// Do something similar with datafile2
if (datafile2.exists())
{
// [...do the same as in the first try/catch block...]
String firstrow = null, lastrow = null;
String row = null;
int i = 0;
do
{
lastrow = row;
row = r.readLine();
if (i == 0)
firstrow = row;
i++;
} while(row != null);
// [...parse firstrow and lastrow into a datastructure...]
}
}

use split
while ((line = bufferReader.readLine()) != null)
{
String[] tokens = line.split(" ");
System.out.println(line + " -> [" + tokens[0] + "]" + "[" + tokens[1] + "][" + tokens[2] + "]");
}
if you must have this in an array you can use the following:
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.text.ParseException;
import java.util.ArrayList;
import java.util.List;
public class NodeTest {
public static void main(String[] args) throws ParseException {
try {
File first = new File("data.txt");
File second = new File("data1.txt");
Node[] nodes1 = getNodes(first);
Node[] nodes2 = getNodes(second);
print(nodes1);
print(nodes2);
}
catch(Exception e) {
System.out.println("Error reading file " + e.getMessage());
}
}
public static final void print(Node[] nodes) {
System.out.println("======================");
for(Node node : nodes) {
System.out.println(node);
}
System.out.println("======================");
}
public static final Node[] getNodes(File file) throws IOException {
FileReader inputHeuristic = new FileReader(file);
BufferedReader bufferReader = new BufferedReader(inputHeuristic);
String line;
List<Node> list = new ArrayList<Node>();
while ((line = bufferReader.readLine()) != null) {
String[] tokens = line.split(" ");
list.add(new Node(tokens[0], tokens[1]));
}
bufferReader.close();
return list.toArray(new Node[list.size()]);
}
}
class Node {
String start;
String end;
public Node(String start, String end){
this.start = start;
this.end = end;
}
public String toString() {
return "[" + start + "][" + end + "]";
}
}

Something like this?
HashSet<String> nodes = new HashSet<String>();
try(BufferedReader br = new BufferedReader(new FileReader("data.txt"))) {
String line = br.readLine();
while (line != null) {
String[] l = line.split(" ");
nodes.add(l[0]);
line = br.readLine();
}
}
try(BufferedReader br = new BufferedReader(new FileReader("data1.txt"))) {
String line = br.readLine();
while (line != null) {
String[] l = line.split(" ");
if (nodes.contains(l[0]) || nodes.contains(l[1]))
// Do whatever you want ...
line = br.readLine();
}
}

Is it possible to read data from file and store it into 2d Array,when we don't know the number of line in the file,in java

I have to read data from file Here is data and want plot a graph vs thick(column 1 in data) and alpha(column 3) for every model. Every model has 7 line data,the last that start with 0 not required. Here is my code. it works but i don't think it is good code.please, suggest me better way to do the same.
public class readFile {
public static int showLines(String fileName) {
String line;
int currentLineNo = 0;
BufferedReader in = null;
try {
in = new BufferedReader (new FileReader(fileName));
//read until endLine
while(((line = in.readLine()) != null)) {
if (!line.contains("M") && !line.contains("#") && !line.trim().startsWith("0")) {
//skipping the line that start with M, # and 0.
currentLineNo++;
}
}
} catch (IOException ex) {
System.out.println("Problem reading file.\n" + ex.getMessage());
} finally {
try { if (in!=null) in.close(); } catch(IOException ignore) {}
}
return currentLineNo;
}
//Now we know the dimension of matrix, so storing data into matrix
public static void readData(String fileName,int numRow) {
String line;
String temp []=null;
String data [][]=new String[numRow][10];
int i=0;
BufferedReader in = null;
try {
in = new BufferedReader (new FileReader(fileName));
//read until endLine
while(((line = in.readLine()) != null)) {
if (!line.contains("M") && !line.contains("#") && !line.trim().startsWith("0")) {
temp=(line.trim().split("[.]"));
for (int j = 0; j<data[i].length; j++) {
data[i][j] =temp[j];
}
i++;
}
}
// Extract one column from 2d matrix
for (int j = 0; j <numRow; j=j+6) {
for (int j2=j; j2 <6+j; j2++) {
System.out.println(Double.parseDouble(data[j2][0])+"\t"+Double.parseDouble(data[j2][2]));
//6 element of every model, col1 and col3
// will add to dataset.
}
}
} catch (IOException ex) {
System.out.println("Problem reading file.\n" + ex.getMessage());
} finally {
try { if (in!=null) in.close(); } catch(IOException ignore) {}
}
}
//Main Method
public static void main(String[] args) {
//System.out.println(showLines("rf.txt"));
readData("rf.txt",showLines("rf.txt") );
}
}

as johnchen902 implies use a list
List<String> input=new ArrayList<String>();
BufferedReader br = new BufferedReader(new FileReader(file));
String line;
while ((line = br.readLine()) != null) {
input.add(line);
}
br.close();
int N=input.get(0).split(",").size(); // here add your delimiter
int M=input.size();
String[][] data=new String[M][N]
for (int i=0;i<M;i++){
String[] parts = string.split("-");
for (int k=0;k<n;k++){
data[i][k]=parts[k];
}
}
something like that
hope it helps. plz put more effort into asking the question. Give us the needed Input files, and the Code you came up with until now to solve the problem yourself.