Develop Reference

How do I get rid of java.lang.NumberFormatException error

This code takes two txt files, reads them puts them in 2d arrays and should check if the numbers in the files are magic squares but it keeps returning NumberFormatException error. I'm new to java so if anyone could help me that would be great. I'm pretty sure the problem come from the txt file being string and the 2d array needing to be in int form. But how and where do I make that conversion on my code?
this is what i have:
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Arrays;
import java.util.Scanner;
public class ms {
public static void main(String[] args) throws FileNotFoundException {
String filename1 = "magicSquaresData.txt", filename2 = "magicSquaresData.txt";
int nos[][] = null;
nos = getArray(filename1);
boolean b = isMagicSquare(nos);
printArray(nos);
if (b) {
System.out.println("It is a magic Square");
} else {
System.out.println("It is not a magic Square");
}
System.out.println("\n");
nos = getArray(filename2);
b = isMagicSquare(nos);
printArray(nos);
if (b) {
System.out.println("It is a magic Square");
} else {
System.out.println("It is not a magic Square");
}
}
private static int[][] getArray(String filename) throws FileNotFoundException {
String line;
int nos[][] = null;
int size = 0, rows = 0;
Scanner sc = null;
try {
sc = new Scanner(new File(filename));
while (sc.hasNext()) {
if (!sc.nextLine().isEmpty())
size++;
}
sc.close();
nos = new int[size][size];
sc = new Scanner(new File(filename));
while (sc.hasNext()) {
line = sc.nextLine();
if (!line.isEmpty()) {
String arr[] = line.split("\t");
for (int i = 0; i < arr.length; i++) {
nos[rows][i] = Integer.valueOf(arr[i]);
}
rows++;
}
}
sc.close();
} catch (FileNotFoundException e) {
System.out.println(e);
}
return nos;
}
private static void printArray(int[][] nos){
for(int i = 0; i<nos[0].length;i++) {
for (int j = 0; j < nos[0].length; j++){
System.out.printf("%-3d",nos[i][j]);
}
System.out.println();
}
}
private static boolean isMagicSquare(int[][] square) {
boolean bool = true;
int order = square.length;
int[] sumRow = new int[order];
int[] sumCol = new int[order];
int[] sumDiag = new int[2];
Arrays.fill(sumRow, 0);
Arrays.fill(sumCol, 0);
Arrays.fill(sumDiag, 0);
for (int row = 0; row < order; row++){
for (int col = 0; col < order; col++) {
sumRow[row] += square[row][col];
}
}
for (int col = 0; col < order; col++) {
for (int row = 0; row < order; row++) {
sumCol[col] += square[row][col];
}
}
for (int row = 0; row < order; row++) {
sumDiag[0] += square[row][row];
}
for (int row = 0; row < order; row++) {
sumDiag[1] += square[row][order - 1 - row];
}
bool = true;
int sum = sumRow[0];
for (int i = 1; i < order; i++) {
bool = bool && (sum == sumRow[i]);
}
for (int i = 0; i < order; i++) {
bool = bool && (sum == sumCol[i]);
}
for (int i = 0; i < 2; i++) {
bool = bool && (sum == sumDiag[i]);
}
return bool;
}
}

SUGGESTION:
Substitute nos[rows][i] = Integer.valueOf(arr[i]); for a custom method that will tell you WHERE the error is occurring.
EXAMPLE:
public static Integer tryParse(String text, int row, int i) {
try {
return Integer.parseInt(text);
} catch (NumberFormatException e) {
System.out.println("ERROR: row=" + row + ", i=" + i + ", text=" + text);
return null;
}
}
CAVEAT: This is for helping you troubleshoot ONLY. You definitely wouldn't want to release this in "production code" ;)

What is the NumberFormatException?
Thrown to indicate that the application has attempted to convert a string to one of the numeric types, but that the string does not have the appropriate format.
Offtopic:
A thing that i can notice is that both filesnames have the same name. So you will verify the same file 2 times.
String filename1 = "magicSquaresData.txt", filename2 = "magicSquaresData.txt";
I checked your program and you error appears when you put like this on a file:
1. 5 5
2. 5 5
So the error shows beacause you are trying to parse to int the String "5 5". So your code pick the all line and tries to convert to int and " " it's not an int. And there lives the NumberFormatException error.
How do to solve it?
The function that we will work on is the one that you pass from file to an array in
private static int[][] getArray(String filename) throws FileNotFoundException{
The of the function is after we read the file.
As you said, you are leading with a 2d array so to insert all the numbers we need to have loops for each dimension on the array.
So we will start from there.
I will use a while beacause we are dealing with a string and it's easier to verify the text that its left on the line. Will add a new int variable that starts in 0 to pass in every column of a line to use with the while loop. And with this we got this:
for (int i = 0; i < lines.length; i++) {
while(!"".equals(line)){
whileIterator++;
}
whileIterator = 0;
}
Next setep, we will divide in 2 behaviors because we will substring the String that has in the line, and will work differently when it's the last number that we are verifying:
for (int i = 0; i < lines.length; i++) {
while(!"".equals(line)){
if(whileIterator + 1 == size){//If its the last iteration that we need in a line
}else{//All other iterations
whileIterator++;
}
whileIterator = 0;}
To finalize let's add the new logic to insert in nos array. So lets pick all line for example 2 7 6 and we want to add the number 2, so lets do that. You just need to substring(int startIndex, int finalIndex) the line and add to the nos array. After that let remove the number and the space ("2 ") from the line that we are veryfying.
for (int i = 0; i < lines.length; i++) {
while(!"".equals(line)){
if(whileIterator + 1 == size){//If its the last iteration that we need
nos[rows][whileIterator] = Integer.parseInt(line.substring(0));//Add to array
line = "";//To not pass the while verification
}else{//All other iterations
nos[rows][whileIterator] = Integer.parseInt(line.substring(0, line.indexOf(" ")));//Add to array
line = line.substring(line.indexOf(" ") + 1);//remove the number we added behind
}
whileIterator++;
}
whileIterator = 0;}
And here you go, that how you add the numbers to an array and don't get the error.
If you need some further explanation just ask. Hope it helps :)

Using an array to input strings, and another one to output word frequency

So I am trying to complete this code. The goal is to input an array of strings, then count the frequency of how often the words are found. For example:
input:
joe
jim
jack
jim
joe
output:
joe 2
jim 2
jack 1
jim 2
joe 2
An array must be chosen for Strings, and another array much be chosen for word frequency.
My code so far:
I am stuck into trying to implement this. The string method is set, but how am I going to count the frequency of words, and also assign those values to an array. Then print both side by side. I do know that once the integer array is set. We can simply do a for loop to print the values together such as. System.out.println(String[i] + " " + countarray[i]);
public class LabClass {
public static int getFrequencyOfWord(String[] wordsList, int listSize, String currWord) {
int freq = 0;
for (int i = 0; i < listSize; i++) {
if (wordsList[i].compareTo(currWord) == 0) {
freq++;
}
}
return freq;
}
public static void main(String[] args) {
LabClass scall = new LabClass();
Scanner scnr = new Scanner(System.in);
// assignments
int listSize = 0;
System.out.println("Enter list Amount");
listSize = scnr.nextInt();
// removing line to allow input of integer
int size = listSize; // array length
// end of assignments
String[] wordsList = new String[size]; // string array
for (int i = 0; i < wordsList.length; i++) { //gathers string input
wordsList[i] = scnr.nextLine();
}
for (int i = 0; i < listSize; i++) {
String currWord = wordsList[i];
int freqCount = getFrequencyOfWord(wordsList, listSize, currWord);
System.out.println(currWord + " " + freqCount);
}
}
}

int some_method(String[] arr, String word) {
int count = 0;
for (int i=0; i<arr.size(); i++) {
if (arr[i].equals(word)) count++;
}
return count;
}
Then in main method:
String[] array = ["joe", "jake", "jim", "joe"] //or take from user input
int[] countArray = new int[array.size()]
for (int i=0; i<array.size(); i++) {
countArray[i] = some_method(array, array[i])
}
System.out.println(array[0] + " " + countArray[0]);
Ouput:
joe 2

How do I count multiple duplicate elements in an ArrayList?

I have a program that takes in a file list of bands and albums. I need to determine the number of album each band makes and then print out a list of the the bands and the number of albums they made in descending order. I have looked around and seen it done using mapping and collections. I want to know how to do it without either. Here is what I have so far:
public static void processFile(String filename)
{
String bandname = "";
String[][] data = read_spreadsheet(filename);
//takes the file and converts it to a 2d array
ArrayList<String> bands = new ArrayList<String>();
for(int rows = 0; rows < data.length; rows++)
{
bands.add(data[rows][0]);
}
for(int i = 0; i<bands.size()-1;i++)
{
int albumcount = 0;
for(int j = i+1; j<bands.size();j++)
{
if(bands.get(i).equals(bands.get(j)))
{
albumcount++;
}
}
}
}
input example:
band1 -album
band2 -album
band1 -album
band3 -album
band1 -album
band2 -album
output example:
band1: 3
band2: 2
band3: 1

Without collections? You want to use arrays?
String [] names = new String[data.length];
int [] counts = new int[data.length];
int j = 0;
for (int i = 0; i < data.lenght; i++ ) {
while (j < data.length) {
if (data[i][0].equals(names[j])) {
found = true;
counts[j]++;
break;
} else if (names[j] == null) {
names[j] = data[i][0];
counts[j]=1;
break;
}
j++;
}
}
// find max count
// println
// nullify element
// repeat
for (int i = 0; i < j; i++) {
int max = -1;
int k = i;
int pos = -1;
while ( k < j ) {
if ( counts[k] > max ) {
pos = k;
max = counts[k];
}
k++;
}
if ( pos != -1 ) { // we found
System.out.println ( names[pos] + ": " + counts[pos]);
counts[pos] = -1;
}
}

If you sort the list of band names (with duplicates) and then count how many of each band name is in the list, you will get the album count for each band:
public static void processFile(String filename)
{
//takes the file and converts it to a 2d array
String[][] data = read_spreadsheet(filename);
// get all the bands (with duplicates)
ArrayList<String> bands = new ArrayList<String>();
for(int rows = 0; rows < data.length; rows++) {
bands.add(data[rows][0]);
}
// sort the bands alphabetically
Collections.sort(bands);
int albumCount = 1;
String currentBand = bands.remove(0);
while(bands.size() > 0) {
String nextBand = bands.remove(0);
if(currentBand.equals(nextBand)) {
albumCount++;
} else {
// print the current band album count and setup for the next band
System.out.println(currentBand + ": " + albumCount);
currentBand = nextBand;
albumCount = 1;
}
};
// print the final band album count
System.out.println(currentBand + ": " + albumCount);
}

Why is there StringOutofBoundException?

My code needs to read information from the textfile. And the textfile looks like this:
X...................
....................
....................
....................
....................
....................
....................
....................
....................
..X.................
Yes, I need to get # of rows and columns and also identify the number and location of 'X's. I'm almost done except my second constructor is giving me a StringOutOfBoundException in the line:
treasureLocations[location] = new Coord(i, j);
I need help only with the second constructor. Could smb please help me with that?
import java.util.Scanner; // Required to get input
import java.io.File; // Required to get input from files
// A 2D treasure map which stores locations of treasures in an array
// of coordinates
public class TreasureMap{
int rows, cols; // How big is the treasure map
Coord [] treasureLocations; // The locations of treasures
Scanner kbd = new Scanner(System.in);
// Prompt the user for info on the treasure map and then create it
// COMPLETE THIS METHOD
public TreasureMap(){
int numberOfTreasures = 0;
System.out.println("Enter map size (2 ints): ");
rows = kbd.nextInt(); cols = kbd.nextInt();
System.out.println("Enter number of treasures (1 int): ");
numberOfTreasures = kbd.nextInt();
treasureLocations = new Coord[numberOfTreasures];
for (int i = 0; i < numberOfTreasures; i++)
{
System.out.println("Enter treasure " + i + " location (2 ints): ");
rows = kbd.nextInt(); cols = kbd.nextInt();
treasureLocations[i] = new Coord(rows, cols);
}
}
// Read the string representation of a map from a file
// COMPLETE THIS METHOD
public TreasureMap(String fileName) throws Exception{
rows = 0;
cols = 0;
int treasures = 0;
char x = 'X';
Scanner data = new Scanner(new File(fileName));
while(data.hasNextLine())
{
String line = data.nextLine();
for (int i = 0; i < line.length(); i++)
{
if(x == line.charAt(i))
{
treasures++;
}
}
cols = line.length();
rows++;
}
int location = 0;
treasureLocations = new Coord[treasures];
Scanner temp = new Scanner (new File(fileName));
while(temp.hasNextLine())
{
String line = temp.nextLine();
for(int i = 0; i < rows; i++)
{
for (int j = 0; j < cols; j++)
{
if(x == line.charAt(j))
{
treasureLocations[location] = new Coord(i, j);
location++;
}
}
}
}
}
// true if there is treasure at the given (r,c) coordinates, false
// otherwise
// This method does not require modification
public boolean treasureAt(int r, int c){
for(int i=0; i<treasureLocations.length; i++){
Coord coord = treasureLocations[i];
if(coord.row == r && coord.col == c){
return true;
}
}
return false;
}
// Create a string representation of the treasure map
// This method does not require modification
public String toString(){
String [][] map = new String[this.rows][this.cols];
for(int i=0; i<rows; i++){
for(int j=0; j<cols; j++){
map[i][j] = ".";
}
}
for(int i=0; i<treasureLocations.length; i++){
Coord c = treasureLocations[i];
map[c.row][c.col] = "X";
}
StringBuilder sb = new StringBuilder();
for(int i=0; i<rows; i++){
for(int j=0; j<cols; j++){
sb.append(map[i][j]);
}
sb.append("\n");
}
return sb.toString();
}
}

You should not use the for i as you do. Your i means the current row, doesn't it? So every time you input a line(temp.nextLine()), your i must be added one.
int i=0;
while(temp.hasNextLine())
{
String line = temp.nextLine();
for (int j = 0; j < cols; j++)
{
if(x == line.charAt(j))
{
treasureLocations[location] = new Coord(i, j);
location++;
}
}
}
++i;
}

I keep getting a line of character as my output for my sum of all years WHY?

Everything that ive done so far is correct, but once i get down to my last print statement i keep getting a string of characters as my answer when i should be getting the sum of all the salaries for the entire array. PLEASE HELP !
my output is
Total money made by person at row 1 is 118943
The total salaries of all individuals is [[I#1540e19d
public class SummerStats
{
private int [][] salaries;
public SummerStats(int numPeople, int numYears)
{
//initialize array
salaries = new int[numPeople][numYears];
java.util.Random r = new java.util.Random();
//fill array
for(int i=0; i<numPeople; i++)
{
for(int j=0; j<numYears; j++)
{
salaries[i][j] = r.nextInt(100000);
}
}
}
public int [][] getSalaries()
{
return salaries;
}
public int getMostMoneyOverYears()
{
int [] tmp = new int[salaries[0].length];
int k = 0;
for(int i=0; i<salaries.length; i++)
{
for(int j=0; j<salaries[i].length; j++)
{
tmp[k] += salaries[i][j];
}
k++;
}
return getMax(tmp);
}
private int getMax(int [] arry)
{
int sal1=0;
int idx=-1;
for(int i=0; i<arry.length; i++)
{
if(sal1 <arry[i])
{
sal1= arry[i];
idx = i;
}
}
return idx;
}
public int getHighestSalary()
{
//find the highest salary in a single year and return of the index
int [][] tmp = new int [salaries.length][2]; //stores salary (row) and the index (col) from the salaries [][]
int max = 0;
int idxtmp = -1;
int p=0;
for(int i=0; i<salaries.length; i++)
{
for(int j=0; j<salaries[i].length; j++)
{
if(max < salaries[i][j])
{
max = salaries[i][j];
idxtmp = j;
}
}
//add max value and its corresponding index to tmp
tmp[p][0] = max;
tmp[p][1] = idxtmp;
p++;
}
//now that we have the max for each person (row) compare salaries in each row
//reset values
max = 0;
idxtmp = -1;
for(int i=0; i<tmp.length; i++)
{
if(max < tmp[i][0])
{
max = tmp[i][0]; //this is the max salary
idxtmp = tmp[i][1]; //this is the index of the salary from the salaries[][]
}
}
return idxtmp;
}
public int getTotalSalary (int person)
{
int totalSalary = 0;
for(int i=0; i<salaries[person].length; i++)
{
totalSalary+=salaries[person][i];
}
return totalSalary;
}
//get total of all salaries
public int getAllSalaries()
{
int sum = 0;
for(int i=0; i<salaries.length; i++)
{
for(int j=0; j < salaries[i].length; j++)
{
sum += salaries[i][j];
}
}
return sum;
}
}
import java.util.Scanner;
public class TestSummerStats
{
public static void main(String [] args)
{
SummerStats ssObj = new SummerStats(2, 3);
int [][] sal = ssObj.getSalaries();
for(int i=0; i<2; i++)
{
for(int j=0; j<3; j++)
{
System.out.println("Salary at " + i + " " + j + " is $" + sal[i][j]);
}
}
//keep my output looking clean
System.out.println();
System.out.println("Index of the big baller: " + ssObj.getMostMoneyOverYears());
//keep my output looking clean
System.out.println();
System.out.println("Index of the year with the highest salary: " + ssObj.getHighestSalary());
//keep my output looking clean
System.out.println();
//promt the user to enter the person that you want the salary for
Scanner scan = new Scanner(System.in);
System.out.println("Please enter the person you want to know the salary for.");
int person = scan.nextInt();
//keep my code clean
System.out.println();
//print out the amount of money made by the specified person
System.out.println("Total money made by person at row " + person + " is " + ssObj.getTotalSalary(person));
//sum the entire salaries
System.out.println("The total salaries of all individuals is " + ssObj.getSalaries());
}
}

The method getSalaries() is declared and defined thusly:
public int [][] getSalaries() {
return salaries;
}
It is defined to return a two dimensional array, and the result you're seeing is the default toString() returned from such a beast. To get an actual number, your method should return a number, perhaps a double or an int, your choice, and inside the method body, you should iterate through your 2-D array summing up all the salaries.

Judging from the text in the last line, you should change the method call in the last line from ssObj.getSalaries() to ssObj.getAllSalaries().
The "string of characters" you are getting is what happens when you convert an array to a String (either implicitly by concatenating with another string or explicitly by calling toString() on the array).

You're calling the function getSalaries() which returns an array. You should be calling ssObj.getAllSalaries().
The string you're getting is probably a reference to the salaries array object.