I'm having some trouble accessing my 2D array (myArray) outside of this the loop. I want to access it using other methods, but I can't even access it in this method. It prints out correctly as it's looping, but the test print of
System.out.println(myArray[10][2]);
is always null. So it's like the array isn't actually filling or something. Anyone know what I'm doing wrong here?
package titanic;
import java.io.*;
import java.util.*;
public class Titanic {
public static final int ROW = 1309;
public static final int COLUMN = 6;
public static String [][] myArray = new String[ROW][COLUMN];
public static String[][] arraySetup(){
int recordCounter = 0;
String[][] myArray = new String[ROW][COLUMN];
String[] name = new String [ROW];
try {
BufferedReader br = new BufferedReader(new FileReader("C:/Users/Tom/Desktop/Titanic.txt"));
String line;
for (int i = 0; i < 1309; i++){
while((line = br.readLine()) != null){
String tmp[] = line.split("\t");
myArray[i][0] = tmp[0];
myArray[i][1] = tmp[1];
myArray[i][2] = tmp[2];
myArray[i][3] = tmp[3];
myArray[i][4] = tmp[4];
myArray[i][5] = tmp[5];
System.out.println("myArray[i][5] = " + myArray[i][5]);
recordCounter++;
}
}
} catch (IOException e) {
e.printStackTrace();
}
System.out.println(myArray[10][2]);
System.out.println(recordCounter + " records.");
return myArray;
}
As you have you while loop inside for loop that is used to for indexing your output array while loop always writes into the myArray[0][0] to myArray[0][5]
for (int i = 0; i < 1309; i++){ // i is 0
while((line = br.readLine()) != null){ // you go through all the lines while i is 0
String tmp[] = line.split("\t");
myArray[i][0] = tmp[0];
myArray[i][1] = tmp[1];
myArray[i][2] = tmp[2];
myArray[i][3] = tmp[3];
myArray[i][4] = tmp[4];
myArray[i][5] = tmp[5];
System.out.println("myArray[i][5] = " + myArray[i][5]);
recordCounter++;
}
}
Because of that your check always returns null.
System.out.println(myArray[10][2]);
I think the problem in your code is right there
for (int i = 0; i < 1309; i++){ // you loop 1308 time
while((line = br.readLine()) != null){ /* in each loop, you loop
until you have read all the file so you read 1308 time the file. But when
you reach the end of file on the first iterration, it wont read the file on the 1307
other iterration and all data will be store in myArray[0][0-5]*/
String tmp[] = line.split("\t");
myArray[i][0] = tmp[0];
myArray[i][1] = tmp[1];
myArray[i][2] = tmp[2];
myArray[i][3] = tmp[3];
myArray[i][4] = tmp[4];
myArray[i][5] = tmp[5];
System.out.println("myArray[i][5] = " + myArray[i][5]);
recordCounter++;
}
}
Don't use for and while loop together. During the first for loop, your while reads all file contents and all other array positions remain empty.
Try this instead:
int i=0;
while ((line = br.readLine()) != null){
String tmp[] = line.split("\t");
myArray[i][0] = tmp[0];
myArray[i][1] = tmp[1];
...
myArray[i][5] = tmp[5];
i++;
System.out.println("myArray[i][5] = " + myArray[i][5]);
recordCounter++;
}
Related
I am attempting to read in info from files to implement Dijkstra's algorithm. I believe that the double for loop is causing this to drastically slow down, is there anyway around this?
Edge[] edge = new Edge[127807];
int indexEdge = 0;
String line2 = "";
BufferedReader fileReader2 = new BufferedReader(new FileReader("Road.txt"));
String valueString = null;
String vertex1IDName = null;
String vertex2IDName = null;
String extra = null;
float value = 0;
int vertex1ID = 0;
int vertex2ID = 0;
//Read the file line by line
while ((line2 = fileReader2.readLine()) != null)
{
//Get all tokens available in line
String[] tokens2 = line2.split(DELIMITER);
for(String token1 : tokens2)
{
vertex1IDName = tokens2[0];
vertex2IDName = tokens2[1];
valueString = tokens2[2];
if(tokens2.length - 1 == 3) {
extra = tokens2[tokens2.length - 1];
}
else {
extra = "";
}
vertex1ID = Integer.parseInt(vertex1IDName);
vertex2ID = Integer.parseInt(vertex2IDName);
value = Float.parseFloat(valueString);
}
System.out.println("value: "+ value + " vertex1ID:"+ vertex1ID +" vertex2ID:"+ vertex2ID+ " extra:" + extra);
//if vertex 1 name or vertex 2 name in vertex.getID()
for(int i = 0; i< indexVertex; i++) {
for(int j = 0; j< indexVertex; j++) {
if(vertex1ID == vertex[i].getID() && vertex2ID == vertex[j].getID()) {
vertex[i].addNeighbour(edge[indexEdge] = new Edge(value,vertex[i],vertex[j],extra));
indexEdge++;
}
}
}
}
I have a .txt file with the next format:
I need to storage that values in this way, at index 0 i need to have
[[154.5,0.0],[13.3333333333333, 102.0],[6,272.0],[10.3333333333333,1860.0]...
(there will be more pairs cause the second column in txt is not ordered, and there will be zeros again later)]. I hope that u understand my question, i think i need arraylist of arraylist of arraylist, i just need an idea, thanks.
This is the code:
String working_directory = System.getProperty("user.dir");
File file = new File(working_directory + "\\src\\" + filename);
BufferedReader br = new BufferedReader(new FileReader(file));
ArrayList<ArrayList<Double>> array_A = new ArrayList<ArrayList<Double>>();
ArrayList<Double> aux = new ArrayList<Double>();
aux.add((double)0);
aux.add((double)0);
for ( int i = 0 ; i < matrixSize; i ++ ) {
array_A.add(aux);
}
String[] elements_in_line = new String[3];
String line;
while ((line = br.readLine()) != null) {
ArrayList<Double> value_col_index = new ArrayList<Double>();
ArrayList<Double> pair = new ArrayList<Double>();
elements_in_line = line.split(", ");
double value = Double.parseDouble(elements_in_line[0]);
int line_index = Integer.parseInt(elements_in_line[1]);
int column_index = Integer.parseInt(elements_in_line[2]);
boolean already_exists = false;
if (array_A.get(line_index).size() > 0) {
pair = array_A.get(line_index);
for (int i = 0; i < pair.size(); i++) {
if (column_index == pair.get(1)) {
already_exists = true;
break;
}
}
}
if (already_exists) {
pair.set(0, pair.get(0) + value);
} else {
if (limit_line != 0) {
if (array_A.get(line_index).size() == limit_line) {
System.out.println("Dimension of matrix exceeded!");
System.exit(1);
}
}
array_A.set(line_index,new ArrayList<Double>(Arrays.asList(value,(double)column_index)));
}
}
return array_A;
}
I have tried so hard to find a solution to this problem! Here is my code:
import java.io.*;
import java.lang.reflect.Array;
import java.util.ArrayList;
public class Weather {
public static void main(String[] args) throws IOException {
//Getting the file.
String fileName = "weather2013.txt";
//Lines!
String line;
//Creating arrayList object
ArrayList aList = new ArrayList();
try {
BufferedReader input = new BufferedReader(new FileReader(fileName));
while ((line = input.readLine()) != null) {
aList.add(line);
}
//Close the file
input.close();
} catch (FileNotFoundException ex) {
System.out.println("File not found!");
}
//Station ID Number:
String firstLine = aList.get(1).toString();
String stationIDStr = firstLine.substring(0, 6);
int StationID = Integer.parseInt(stationIDStr);
//System.out.println(StationID);
//WBAN ID Number:
String wbanIDstr = firstLine.substring(7, 12);
int wbanID = Integer.parseInt(wbanIDstr);
//System.out.println(wbanID);
//Year!
String yearStr = firstLine.substring(12, 18).trim();
int year = Integer.parseInt(yearStr);
//System.out.println(year);
//Remove line of text (not needed)
aList.remove(0);
//Fog days:
int fogDays = 0;
for (int i = 0; i < aList.size(); i++) {
String listString = aList.get(i).toString(); //iterate each readLINE -> String
String lastDigits = listString.substring(132, 137); //Each entry from 132-137 only
char fogIndicator = lastDigits.charAt(0);
if (fogIndicator == '1') {
fogDays++;
}
}
//System.out.println(fogDays);
//Maximum and minimum average temps
for (int i = 0; i < aList.size(); i++) {
String listString = aList.get(i).toString();
String averageTempDigits = listString.substring(24, 30).trim();
}
}
}
The specific part of the code where I am having trouble is the VERY last for loop.
Here's what's being outputted:
47.9
41.8
.
.
.
.
41.8
67.0
66.5
I would like to know how to get this column above into an Array or ArrayList?
I want to search in an arraylist from a user input but my if condition doesn't seem to work. Using boolean and .contains() doesn't work for my programme either. This is the coding:
String phone;
phone=this.text1.getText();
System.out.println("this is the phone: " + phone);
BufferedReader line = new BufferedReader(new FileReader(new File("C:\\Users\\Laura Sutardja\\Documents\\IB DP\\Computer Science HL\\cs\\data.txt")));
String indata;
ArrayList<String[]> dataArr = new ArrayList<String[]>();
while ((indata = line.readLine()) != null) {
String[] club = new String[2];
String[] value = indata.split(",", 2);
//for (int i = 0; i < 2; i++) {
int n = Math.min(value.length, club.length);
for (int i = 0; i < n; i++) {
club[i] = value[i];
}
boolean aa = dataArr.contains(this.text1.getText());
if(aa==true)
text2.setText("The data is found.");
else
text2.setText("The data is not found.");
dataArr.add(club);
}
for (int i = 0; i < dataArr.size(); i++) {
for (int x = 0; x < dataArr.get(i).length; x++) {
System.out.printf("dataArr[%d][%d]: ", i, x);
System.out.println(dataArr.get(i)[x]);
}
}
}
catch ( IOException iox )
{
System.out.println("Error");
}
Your dataArr is a list of String[], and you are searching for a String. The two are different kind of objects.
I don't really know how the content of the club array looks like, but you should either change dataArr in order to hold plain String, or to write a method which looks iteratively in dataArr for a String[] containing the output of this.text1.getText().
There is a lot wrong with the program. I assume you want to read a textfile and store each line in the arraylist. To do this you have to split each line of the textfile and store that array in the arrayList.
String[] value;
while ((indata = line.readLine()) != null) {
value = indata.split(",");
dataArr.add(value);
}
Now you have the contents of the file in the arrayList.
Next you want to compare the userinput with each element of the arraylist.
int j = 0;
for (int i = 0; i < dataArr.size(); i++) {
String[] phoneData = dataArr.get(i);
if (phoneData[1].equals(phone)) { // i am assuming here that the phone number is the 2nd element of the String[] array, since i dont know how the textfile looks.
System.out.println("Found number.");
club[j++] = phoneData[1];
} else if (i == dataArr.size()-1) {
System.out.println("Didn't find number.");
}
}
Edit:
As requested:
String phone;
phone = "38495";
System.out.println("this is the phone: " + phone);
BufferedReader line = new BufferedReader(new FileReader(new File("list.txt")));
String indata;
ArrayList<String[]> dataArr = new ArrayList<>();
String[] club = new String[2];
String[] value;// = indata.split(",", 2);
while ((indata = line.readLine()) != null) {
value = indata.split(",");
dataArr.add(value);
}
int j = 0;
for (int i = 0; i < dataArr.size(); i++) {
String[] phoneData = dataArr.get(i);
if (phoneData[1].equals(phone)) {
System.out.println("Found number.");
club[j++] = phoneData[1];
break;
} else if (i == dataArr.size()-1) {
System.out.println("Didn't find number.");
}
}
I hope this makes sense now.
Any ideas what I am missing here? I am reading from a file array. The values in the text file don't get stored and there is no output. All I get is "names and totals" but no values.
I don't know.
private int[] totals;
private String[] names;
private String[] list;
private int count;
public void readData() throws IOException {
BufferedReader input = new BufferedReader(new FileReader("cookies.txt"));
//create the arrays
totals = new int[count];
names = new String[count];
list = new String[count];
//read in each pair of values
String quantityString = input.readLine();
for (int i = 0; i < count; i++) {
names[i] = input.readLine();
list[i] = input.readLine();
quantityString = input.readLine();
totals[i] = Integer.parseInt(quantityString);
}
}
public void display() {
System.out.println("names totals")
for (int i = 0; i < count; i++)
System.out.println(list[i] + " \t " + names[i] + " \t" + totals[i]);
}
//called to compute and print the result
public void printResults() {
//find the best teacher
int maxIndex = 0;
int maxValue = 0;
//for each record stores
for (int i = 0; i < count; i++) {
//if we have a new MAX value so far, update variables
if (maxValue < totals[i]) {
maxValue = totals[i];
maxIndex = i;
}
}
}
You never give the variable count a value, so it initialized to 0 by Java. This means that your arrays are of size 0 also.
So since count is zero, you never read anything from the file, which is why nothing is stored in your arrays and also why nothing is printed out.
Example: Reading a File line-by-line
// create temporary variable to hold what is being read from the file
String line = "";
// when you don't know how many things you have to read in use a List
// which will dynamically grow in size for you
List<String> names = new ArrayList<String>();
List<Integer> values = new ArrayList<Integer>();
// create a Reader, to read from a file
BufferedReader input = new BufferedReader(new FileReader("cookies.txt"));
// read a full line, this means if you line is 'Smith 36'
// you read both of these values together
while((line = input.readLine()) != null)
{
// break 'Smith 36' into an array ['Smith', '36']
String[] nameAndValue = line.split("\\s+");
names.add(nameAndValue[0]); // names.add('Smith')
values.add(Integer.parseInt(nameAndValue[1]); // values.add(36);
}