We Keep Coding

Storing values from a Hash Map into a Text File

I have created a class that allows the user to create and store compounds into a Hash Map and now I want to create another class that allows me to take the values stored in that Hash Map and save them into a text file. I'm not sure if this is needed, but here is the code for the first class that I created containing the Hash Map:
package abi;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
public class ChemicalComp {
public static void main(String[] args) throws IOException{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
Map<String, String> data = new HashMap<String, String>();
while(true){
String readinput=br.readLine();
if(readinput.equals(""))
break;
String input = readinput.replaceAll("\"", "");
String array[]=input.split(", ");
String compound=array[0];
String formula="";
for(int i=1;i<array.length;i++){
if(!array[i].equals("1")){
formula+=array[i];
}
}
data.put(compound, formula);
}
if(!data.isEmpty()) {
#SuppressWarnings("rawtypes")
Iterator it = data.entrySet().iterator();
while(it.hasNext()) {
#SuppressWarnings("rawtypes")
Map.Entry obj = (Entry) it.next();
System.out.println(obj.getKey()+":"+obj.getValue());
}
}
}
}
I'm not too familiar with text files, but I have done some research and this is what I've gotten so far. I know its pretty basic and that I will probably need some type of getter method, but I'm not sure where to incorporate it into what I have. Here is what I have for the class containing the text file:
package abi;
import java.io.FileWriter;
import java.io.PrintWriter;
import java.io.IOException;
public class CompoundManager {
private String path;
private boolean append_to_file = false;
public CompoundManager(String file_path) {
path = file_path;
}
public CompoundManager(String file_path, boolean append_value){
path = file_path;
append_to_file = append_value;
}
public void WriteToFile (String textLine) throws IOException{
FileWriter Compounds = new FileWriter(path, append_to_file);
PrintWriter print_line = new PrintWriter (Compounds);
print_line.printf("%s" + "%n", textLine);
print_line.close();
}
}

I can't understand what your program does but you can use a buffered writer for it.
Just create a try-catch block and wrap a filewriter in a bufferedwriter like this :
try (BufferedWriter br = new BufferedWriter(new FileWriter(new File("filename.txt"))))
{
for (Map.Entry<Integer, String> entry : map.entrySet()) {
int key = entry.getKey();
String value = entry.getValue();
br.write(key + ": " + value);
br.newLine();
}
} catch (Exception e) {
printStackTrace();
}

Creating an Arrylist in a Arraylist in Java

This is my first post so sorry if I mess something up or if I am not clear enough. I have been looking through online forums for several hours and spend more trying to figure it out for myself.
I am reading information from a file and I need a loop that creates an ArrayList every time it goes through.
static ArrayList<String> fileToArrayList(String infoFromFile)
{
ArrayList<String> smallerArray = new ArrayList<String>();
//This ArrayList needs to be different every time so that I can add them
//all to the same ArrayList
if (infoFromFile != null)
{
String[] splitData = infoFromFile.split(":");
for (int i = 0; i < splitData.length; i++)
{
if (!(splitData[i] == null) || !(splitData[i].length() == 0))
{
smallerArray.add(splitData[i].trim());
}
}
}
The reason I need to do this is that I am creating an app for a school project that reads questions from a delimited text file. I have a loop earlier that reads one line at a time from the text. I will insert that string into this program.
How do I make the ArrayList smallerArray a separate ArrayList everytime it goes through this method?
I need this so I can have an ArrayList of each of these ArrayList

Here is a sample code of what you intend to do -
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Stream;
public class SimpleFileReader {
private static final String DELEMETER = ":";
private String filename = null;
public SimpleFileReader() {
super();
}
public SimpleFileReader(String filename) {
super();
setFilename(filename);
}
public String getFilename() {
return filename;
}
public void setFilename(String filename) {
this.filename = filename;
}
public List<List<String>> getRowSet() throws IOException {
List<List<String>> rows = new ArrayList<>();
try (Stream<String> stream = Files.lines(Paths.get(filename))) {
stream.forEach(row -> rows.add(Arrays.asList(row.split(DELEMETER))));
}
return rows;
}
}
And, here is the JUnit test for the above code -
import static org.junit.jupiter.api.Assertions.fail;
import java.io.IOException;
import java.util.List;
import org.junit.jupiter.api.Test;
public class SimpleFileReaderTest {
public SimpleFileReaderTest() {
super();
}
#Test
public void testFileReader() {
try {
SimpleFileReader reader = new SimpleFileReader("c:/temp/sample-input.txt");
List<List<String>> rows = reader.getRowSet();
int expectedValue = 3; // number of actual lines in the sample file
int actualValue = rows.size(); // number of rows in the list
if (actualValue != expectedValue) {
fail(String.format("Expected value for the row count is %d, whereas obtained value is %d", expectedValue, actualValue));
}
} catch (IOException e) {
e.printStackTrace();
}
}
}

Calling method from different class (different than other questions)

So I'm relatively new to java and I'm trying to use a method from a different class inside my main.
The method I'm using to pull doesn't contain any data initially but pulls the data from a text doc.
I've included the code that calls the other class method that loads the data from the file. It sill doesn`t work, so where is my mistake?
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class FinalRobert {
public static void main(String[] args) {
//output of animalList class here
}
Here is the class I'm trying to pull from:
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.FileNotFoundException;
import java.io.IOException;
public class animalList {
public void animalDetails () {
int i = 0;
String animalInfo = "C:/Users/Robert/Documents/animals.txt";
String animalHabitat = "‪C:/Users/Robert/Documents/habitats.txt";
try {
File animalFile = new File(animalInfo);
FileReader animalReader = new FileReader(animalFile);
BufferedReader animalList = new BufferedReader (animalReader);
StringBuilder animalDetailList = new StringBuilder();
String line;
while ((line = animalList.readLine()) != null) {
for (i = 0; i <4 ; i++) {
System.out.println(line);
animalList.readLine();
}
}
animalReader.close();
System.out.println(animalDetailList.toString());
}
catch (IOException e) {
}
}
}
So I want to have the output of the animalList class in my main, but I don't know how to bring it over because I'm not necessarily bring over variable, but a process. The full thing should bring the first line and four past it (so a total of the first five lines in the doc). Hopefully that makes things easier to see my problem.

This is a mcve of AnimalList :
public class AnimalList {//use java naming convention
public void animalDetails () {
//mcve should be runnable. The problem you ask help with is not
//reading from file, so remove file reading functionality to make it mcve
StringBuilder animalDetailList = new StringBuilder();
animalDetailList.append("Family: Cats").append("\n")
.append("Type : Panther").append("\n")
.append("Weight: 250kg").append("\n")
.append("Color : Pink");
System.out.println(animalDetailList.toString());
}
}
Invoke its method from another class:
public class FinalRobert {
public static void main(String[] args) {
//to invoke animalDetails() method use
AnimalList aList = new AnimalList();
aList.animalDetails();
//if you do not need the aList refrence you could use
//new AnimalList().animalDetails();
}
}
Output
Family: Cats Type : Panther Weight: 250kg Color :
Pink

I hope this might help you.
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class FinalRobert {
public static void main(String[] args) {
animalList list = new animalList();
list.animalDetails();
}
}
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.FileNotFoundException;
import java.io.IOException;
public class animalList {
public String animalDetails () {
int i = 0;
String output="";
String animalInfo = "C:/Users/Robert/Documents/animals.txt";
String animalHabitat = "‪C:/Users/Robert/Documents/habitats.txt";
try {
File animalFile = new File(animalInfo);
FileReader animalReader = new FileReader(animalFile);
BufferedReader animalList = new BufferedReader (animalReader);
String line;
while ((line = animalList.readLine()) != null & i<4) {
System.out.println(line);
output = output + "\n"+ line;
i++;
}
animalReader.close();
System.out.println(output);
}
catch (IOException e) {
}
return output;
}
}

Reading numbers from a file and creating an array (java)

I cannot figure out how to make this txt file with numbers into an array, I am able to get it to read and print the screen but I need to be able to organize the numbers and delete the duplicates. This is what my code looks like so far
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
public class File {
public static void main(String[] args) {
String filename = "C:/input.txt";
File rfe = new File();
rfe.readFile(filename);
}
private void readFile(String name) {
String input;
try (BufferedReader reader = new BufferedReader(new FileReader(name))) {
while((input = reader.readLine()) != null) {
System.out.format(input); // Display the line on the monitor
}
}
catch(FileNotFoundException fnfe) {
}
catch(IOException ioe) {
}
catch(Exception ex) { // Not required, but a good practice
}
}
}

I would recommend using an ArrayList rather than an Array.
With an array you would have to parse through the list and calculate the line count before you could even initialize it. An ArrayList is much more flexible as you don't have to declare how many values will be added to it.
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
public class File {
private List<Integer> data = new ArrayList<Integer>(); //Create ArrayList
public static void main(String[] args) {
String filename = "C:/input.txt";
File rfe = new File();
rfe.readFile(filename);
}
private void readFile(String name) {
String input;
try (BufferedReader reader = new BufferedReader(new FileReader(name))) {
while((input = reader.readLine()) != null) {
data.add(Integer.parseInt(input));//Add each parsed number to the arraylist
System.out.println(input); // Display the line on the monitor
}
}
catch(FileNotFoundException fnfe) {
}
catch(IOException ioe) {
}
catch(Exception ex) { // Not required, but a good practice
ex.printstacktrace(); //Usually good for general handling
}
}
}

File always seems to be empty

Ok, I'm really confused by some code I wrote. It's a DataSetter (didn't know a better name for it...), and has methods to change the data in my data file (data.txt). This data has the following format: #key=value (eg. #version=1.0). Now, I tried to run this line of code:
new DataSetter().setValue("version", "1.1");
It just clears the file. That's pretty much all it does. Now, I think it clears the file because it makes a new File, which is completely empty but has the same name. Here's my code:
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Scanner;
/**
* This class contains methods to set specific data in the data.txt file. <br>
* The data is rewritten every time a new value is set.
*
* #author Casper van Battum
*
*/
public class DataSetter {
private static final File DATA_FILE = new File("resources/data.txt");
private static final String lineFormat = "#%s=%s";
private FileOutputStream out;
private DataReader reader = new DataReader();
private HashMap<String, String> dataMap = reader.getDataMap();
private Scanner scanner;
public DataSetter() {
try {
out = new FileOutputStream(DATA_FILE, false);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
public void setValue(String key, String newValue) {
openDataFile();
String oldLine = String.format(lineFormat, key, dataMap.get(key));
dataMap.put(key, newValue);
String newLine = String.format(lineFormat, key, newValue);
try {
replace(oldLine, newLine);
} catch (IOException e) {
e.printStackTrace();
}
closeDataFile();
}
private void replace(String oldLine, String newLine) throws IOException {
ArrayList<String> tmpData = new ArrayList<String>();
while (scanner.hasNextLine()) {
String currentLine = scanner.nextLine();
tmpData.add((currentLine == oldLine) ? newLine : currentLine);
}
out.write(new String().getBytes());
String sep = System.getProperty("line.separator");
StringBuffer sb = new StringBuffer();
for (String string : tmpData) {
sb.append(string + sep);
}
FileWriter writer = new FileWriter(DATA_FILE);
String outString = sb.toString();
writer.write(outString);
writer.close();
}
private void openDataFile() {
try {
scanner = new Scanner(DATA_FILE);
} catch (FileNotFoundException ex) {
ex.printStackTrace();
}
}
private void closeDataFile() {
scanner.close();
}
}
So after running the setValue() method, I just have an empty file...
Im really out of idea's on how to solve this...

You are truncating your data file with the
new FileOutputStream(DATA_FILE, false)
so no nothing is written when you go to output your the elements in the tmpData ArrayList read from Scanner.
ArrayList<String> tmpData = new ArrayList<String>();
while (scanner.hasNextLine()) {
String currentLine = scanner.nextLine(); // never gets called
...
}
The typical strategy for updating a text file is to create a temporary file with old file's contents (File#renameTo), write the data to file, then delete the temporary file after closing any open streams to the file being read.