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How can I read a file from a path relative of my Main class in Java?

On the same directory of my Main.java file, I have a package/folder named database, and inside the database package I have a file named Data.txt.
This is my code of Main.java, but it is throwing this error:
java: exception java.io.FileNotFoundException
How can I get the file from a relative file? I'm used to web development, and usually something with a . dot like "./folder/file.txt" works.
import java.io.File;
import java.util.Scanner;
import java.io.FileNotFoundException;
public class Main {
public static void main(String[] args) {
readFile();
}
public static void readFile() {
File file = new File("./database/Data.txt");
Scanner scanner = new Scanner(file);
try {
while (scanner.hasNextLine()) {
int i = scanner.nextInt();
System.out.println(i);
}
scanner.close();
}
catch (FileNotFoundException e) {
e.printStackTrace();
}
}
}

You are not importing FileNotFoundException class. also, scanner statement throws the exception which should inside try. Solution is as below.
import java.io.File;
import java.util.Scanner;
import java.io.FileNotFoundException;
public class Main {
public static void main(String[] args) {
readFile();
}
public static void readFile() {
File file = new File("database/Data.txt");
try {
Scanner scanner = new Scanner(file);
while (scanner.hasNextLine()) {
int i = scanner.nextInt();
System.out.println(i);
}
scanner.close();
}catch (FileNotFoundException e) {
e.printStackTrace();
}
}
}
Only check if those content can read using scanner or not. Content having int properly. otherwise it will throw java.util.InputMismatchException.

Are you working on a mac or windows system.
I am on windows and ".\database\Data.txt" would most probably work depending on where the file is in your file structure.

SnakeYaml Error Exception in parsing org.yaml.snakeyaml.error.YAMLException: Unable to find property 'First' on class: JavaBeanObject

can someone tell me the error in my SnakeYaml usage v1.19. Somehow it cannot serialize the object and I do not know why.
my JavaBeanObject.java
import org.yaml.snakeyaml.Yaml;
import org.yaml.snakeyaml.constructor.Constructor;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.Paths;
public class ConfigRunner {
private static File myfile = new File(Paths.get(System.getProperty("user.home"),"config", "trial.yml").toString());
private static String mypath =myfile.getPath();
private JavaBeanObject myparam;
public static JavaBeanObject getConfiguration(String filePath) throws IOException{
Constructor constructor = new Constructor(JavaBeanObject.class);
Yaml yaml = new Yaml(constructor);
try (InputStream in = Files.newInputStream(Paths.get(filePath))) {
JavaBeanObject config = yaml.loadAs(in, JavaBeanObject.class);
System.out.println(config.toString());
return config;
}
}
public static void main(String[] args) {
try {
System.out.println(mypath);
getConfiguration(mypath);
} catch (IOException e) {
e.printStackTrace();
}
}
}
My ConfigRunner:
import org.yaml.snakeyaml.Yaml;
import org.yaml.snakeyaml.constructor.Constructor;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.Paths;
public class ConfigRunner {
private static File myfile = new File(Paths.get(System.getProperty("user.home"),"config", "trial.yml").toString());
private static String mypath =myfile.getPath();
private JavaBeanObject myparam;
public static JavaBeanObject getConfiguration(String filePath) throws IOException{
Constructor constructor = new Constructor(JavaBeanObject.class);
Yaml yaml = new Yaml(constructor);
try (InputStream in = Files.newInputStream(Paths.get(filePath))) {
JavaBeanObject config = yaml.loadAs(in, JavaBeanObject.class);
System.out.println(config.toString());
return config;
}
}
public static void main(String[] args) {
try {
System.out.println(mypath);
getConfiguration(mypath);
} catch (IOException e) {
e.printStackTrace();
}
}
}
My trial.yml
First: anton
Second: berta
Third: caesar
Fourth: Dora
Ok, the Problem I am facing here is with the Stringbuilder and it cannot serialize the object. The error that I get is:
C:\Users\domino\config\trial.yml
Exception in thread "main" Cannot create property=First for JavaBean=First: null
First: null
Second: null
Third: null
Fourth: null
in 'reader', line 1, column 1:
First: 'anton ...
^
at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.constructJavaBean2ndStep(Constructor.java:313)
at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.construct(Constructor.java:190)
at org.yaml.snakeyaml.constructor.Constructor$ConstructYamlObject.construct(Constructor.java:346)
at org.yaml.snakeyaml.constructor.BaseConstructor.constructObject(BaseConstructor.java:182)
at org.yaml.snakeyaml.constructor.BaseConstructor.constructDocument(BaseConstructor.java:141)
at org.yaml.snakeyaml.constructor.BaseConstructor.getSingleData(BaseConstructor.java:127)
at org.yaml.snakeyaml.Yaml.loadFromReader(Yaml.java:450)
at org.yaml.snakeyaml.Yaml.loadAs(Yaml.java:444)
at ConfigRunner.getConfiguration(ConfigRunner.java:26)
Caused by: org.yaml.snakeyaml.error.YAMLException: Unable to find property 'First' on class: JavaBeanObject
at org.yaml.snakeyaml.introspector.PropertyUtils.getProperty(PropertyUtils.java:132)
at org.yaml.snakeyaml.introspector.PropertyUtils.getProperty(PropertyUtils.java:121)
at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.getProperty(Constructor.java:323)
at org.yaml.snakeyaml.constructor.Constructor$ConstructMapping.constructJavaBean2ndStep(Constructor.java:241)
at ConfigRunner.main(ConfigRunner.java:36)
Can someone help explain the error?

Exception in thread "main" java.lang.IllegalAccessError: [duplicate]

This question already has an answer here:
Apache POI Parsing error
(1 answer)
Closed 7 years ago.
I am getting the below Exception when I am trying to read an Excel file:
Exception in thread "main" java.lang.IllegalAccessError: tried to access method org.apache.poi.util.POILogger.log(ILjava/lang/Object;)V from class org.apache.poi.openxml4j.opc.PackageRelationshipCollection
at org.apache.poi.openxml4j.opc.PackageRelationshipCollection.parseRelationshipsPart(PackageRelationshipCollection.java:304)
at org.apache.poi.openxml4j.opc.PackageRelationshipCollection.<init>(PackageRelationshipCollection.java:156)
at org.apache.poi.openxml4j.opc.PackageRelationshipCollection.<init>(PackageRelationshipCollection.java:124)
at org.apache.poi.openxml4j.opc.PackagePart.loadRelationships(PackagePart.java:559)
at org.apache.poi.openxml4j.opc.PackagePart.<init>(PackagePart.java:112)
at org.apache.poi.openxml4j.opc.PackagePart.<init>(PackagePart.java:83)
at org.apache.poi.openxml4j.opc.PackagePart.<init>(PackagePart.java:128)
at org.apache.poi.openxml4j.opc.ZipPackagePart.<init>(ZipPackagePart.java:78)
at org.apache.poi.openxml4j.opc.ZipPackage.getPartsImpl(ZipPackage.java:218)
at org.apache.poi.openxml4j.opc.OPCPackage.getParts(OPCPackage.java:662)
at org.apache.poi.openxml4j.opc.OPCPackage.open(OPCPackage.java:223)
at org.apache.poi.openxml4j.opc.OPCPackage.open(OPCPackage.java:186)
at readAndWriteToExcel.ReadingExcel.main(ReadingExcel.java:36)
My code is:
package readAndWriteToExcel;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Map;
import org.apache.commons.io.IOUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.poi.openxml4j.exceptions.InvalidFormatException;
import org.apache.poi.openxml4j.opc.OPCPackage;
public class ReadingExcel {
private static final Log LOG = LogFactory
.getLog(ReadingExcel.class);
public static void main(String[] args) throws Exception {
String SAMPLE_PERSON_DATA_FILE_PATH = "C:/Users/Documents/Test Data 5.xlsx";
File file = new File(SAMPLE_PERSON_DATA_FILE_PATH);
InputStream inputStream = new FileInputStream(file);
// The package open is instantaneous, as it should be.
OPCPackage pkg = null;
try {
ExcelWorkSheetRowCallbackHandler sheetRowCallbackHandler = new ExcelWorkSheetRowCallbackHandler(
new ExcelRowContentCallback() {
public void processRow(int rowNum, Map<String, String> map) {
// Do any custom row processing here, such as save
// to database
// Convert map values, as necessary, to dates or
// parse as currency, etc
System.out.println("rowNum=" + rowNum + ", map=" + map);
}
});
pkg = OPCPackage.open(inputStream);
ExcelSheetCallBack sheetCallback = new ExcelSheetCallBack() {
private int sheetNumber = 0;
public void startSheet(int sheetNum) {
this.sheetNumber = sheetNum;
System.out.println("Started processing sheet number=" + sheetNumber);
}
public void endSheet() {
System.out.println("Processing completed for sheet number=" + sheetNumber);
}
};
System.out.println("Constructor: pkg, sheetRowCallbackHandler, sheetCallback");
ExcelReader example1 = new ExcelReader(pkg,
sheetRowCallbackHandler, sheetCallback);
example1.process();
System.out.println("nConstructor: filePath, sheetRowCallbackHandler, sheetCallback");
ExcelReader example2 = new ExcelReader(SAMPLE_PERSON_DATA_FILE_PATH, sheetRowCallbackHandler, sheetCallback);
example2.process();
System.out.println("nConstructor: file, sheetRowCallbackHandler, sheetCallback");
ExcelReader example3 = new ExcelReader(file,
sheetRowCallbackHandler, null);
example3.process();
} catch (RuntimeException are) {
LOG.error(are.getMessage(), are.getCause());
} catch (InvalidFormatException ife) {
LOG.error(ife.getMessage(), ife.getCause());
} catch (IOException ioe) {
LOG.error(ioe.getMessage(), ioe.getCause());
} finally {
IOUtils.closeQuietly(inputStream);
try {
if (null != pkg) {
pkg.close();
}
} catch (IOException e) {
// just ignore IO exception
}
}
}
}
Is there a simple way to read and edit an Excel file (xls and xlsx) with more than 50k records? I have searched a lot and worked with a few available codes.
But I was not successful, I keep ending up with one Exception or another.

I was getting the same error:
"Handler processing failed; nested exception is
java.lang.IllegalAccessError: tried to access method
org.apache.poi.util.POILogger.log(ILjava/lang/Object;)V from class
org.apache.poi.openxml4j.opc.PackageRelationshipCollection"
After updating maven and trying to access PackageRelationshipCollection and POILogger classes in eclipse things worked fine for me. Make sure you have all the required jars i.e poi, poi-ooxml, poi-ooxml-schemas.

Reading from text file to load images from resource folder

I wanted to make a way so that I can load all the Images in my source folder without having to code each line for each image, but I keep getting an error and have tried different ways to do this and I still can't figure it out. Is it just impossible?
Here is how it works: I save all the images I am going to need on a text file (in this case startUp.txt), then I store the lines in the text file in a linked-list(String) then I use a loop to get the images and store those in a linked-list(Image) so that I don't need to write code for every single Image to load.
Here is my code:
package com.game.task;
import java.awt.Image;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.LinkedList;
import java.util.Scanner;
import javax.swing.ImageIcon;
public class imagesTest {
public LinkedList<Image> storeImages = new LinkedList<Image>();
private LinkedList<String> storeStrings = new LinkedList<String>();
public imagesTest() {
load();
readimage();
}
public void readimage() {
for(int index = 0; index < storeStrings.size(); index++){
Image temp = new ImageIcon(this.getClass().getClassLoader().getResource("/res/"+storeStrings.get(index))).getImage();
storeImages.add(temp);
}
}
private void load() {
File file = new File("Data/startUp.txt");
try {
Scanner read = new Scanner(file);
while (read.hasNextLine()) {
storeStrings.add(read.nextLine());
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
public static void main(String[] arsg) {
imagesTest t = new imagesTest();
}
}
Exception:
Exception in thread "main" java.lang.NullPointerException
at javax.swing.ImageIcon.<init>(ImageIcon.java:217)
at com.game.task.imagesTest.readimage(imagesTest.java:24)
at com.game.task.imagesTest.load(imagesTest.java:41)
at com.game.task.imagesTest.<init>(imagesTest.java:17)
at com.game.task.imagesTest.main(imagesTest.java:45)

I found a way to loop through the resource folder and it was not that hard.
All i had to do use make a method and keep calling it in a loop here is the code
package com.game.task;
import java.awt.Image;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.LinkedList;
import java.util.Scanner;
import javax.swing.ImageIcon;
public class imagesTest {
public LinkedList<Image> storeImages = new LinkedList<Image>();
private LinkedList<String> storeStrings = new LinkedList<String>();
public imagesTest() {
load();
start();
}
public void readimage(String f) {
Image temp = new ImageIcon(this.getClass().getResource("/res/"+f)).getImage();//looks for it
storeImages.add(temp);//put it in a linked-List(Image)
}
public void start(){
for(int index = 0; index < storeStrings.size(); index++){
readimage(storeStrings.get(index));//calling the methode to look in resource folder
}
}
//reads the text file and puts the out put in a linked-list(String)
private void load() {
File file = new File("Data/startUp.txt");
try {
Scanner read = new Scanner(file);
while (read.hasNextLine()) {
storeStrings.add(read.nextLine());
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
public static void main(String[] arsg) {
imagesTest t = new imagesTest();
}
}

Unable to accept filenames as arguments for reading from (or writing to) a file

The following program is meant to read from a file:-
import java.util.*;
import java.io.*;
import java.lang.*;
public class file_read
{
private Scanner input = new Scanner(System.in);
private Scanner fileinput;
public void open() // [1]
{
try
{
String filename = input.next();
fileinput = new Scanner(new File(filename+".txt")); // [2]
}
catch(Exception e)
{
System.out.println("opening error.");
}
}
public void read()
{
// some task to read the file
}
public void closeFile()
{
// closing the file
}
}
Problem lies with [1] and I think that the statement [2] is creating the problem. If I replace the filename+".txt" with the actual filename, everything runs fine. I am unable to pinpoint the reason. Please help.