Ok, so this is what's going on. I'm trying to learn how to use vscode (switching over from jgrasp). I'm trying to run this old school assignment that requires the use of outside .txt files. The .txt files, as well as other classes that I have written are in the same folder and everything. When I try to run this program in JGrasp, it works fine. Though, in VSCode, I get an exception. Not sure what is going wrong here. Thanks Here is an example:
import java.io.*;
public class HangmanMain {
public static final String DICTIONARY_FILE = "dictionary.txt";
public static final boolean SHOW_COUNT = true; // show # of choices left
public static void main(String[] args) throws FileNotFoundException {
System.out.println("Welcome to the cse143 hangman game.");
System.out.println();
// open the dictionary file and read dictionary into an ArrayList
Scanner input = new Scanner(new File(DICTIONARY_FILE));
List<String> dictionary = new ArrayList<String>();
while (input.hasNext()) {
dictionary.add(input.next().toLowerCase());
}
// set basic parameters
Scanner console = new Scanner(System.in);
System.out.print("What length word do you want to use? ");
int length = console.nextInt();
System.out.print("How many wrong answers allowed? ");
int max = console.nextInt();
System.out.println();
//The rest of the program is not shown. This was included just so you guys could see a little bit of it.
If you're not using a project, jGRASP makes the working directory for your program the same one that contains the source file. You are creating the file with a relative path, so it is assumed to be in the working directory. You can print new File(DICTIONARY_FILE).getAbsolutePath() to see where VSCode is looking (probably a separate "classes" directory) and move your data file there, or use an absolute path.
Related
I am currently writing my bachelor thesis and I am using the POI Event API from Apache. In short, my work is about a more efficient way to read data from Excel.
I get asked by developers again and again how exactly this is meant with Event API. Unfortunately I don't find anything on the Apache page about the basic principle.
Following code, how I use the POI Event API (This is from the Apache example for XSSF and SAX):
import java.io.InputStream;
import java.util.Iterator;
import org.apache.poi.ooxml.util.SAXHelper;
import org.apache.poi.openxml4j.opc.OPCPackage;
import org.apache.poi.xssf.eventusermodel.XSSFReader;
import org.apache.poi.xssf.model.SharedStringsTable;
import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;
import javax.xml.parsers.ParserConfigurationException;
public class ExampleEventUserModel {
public void processOneSheet(String filename) throws Exception {
OPCPackage pkg = OPCPackage.open(filename);
XSSFReader r = new XSSFReader( pkg );
SharedStringsTable sst = r.getSharedStringsTable();
XMLReader parser = fetchSheetParser(sst);
// To look up the Sheet Name / Sheet Order / rID,
// you need to process the core Workbook stream.
// Normally it's of the form rId# or rSheet#
InputStream sheet2 = r.getSheet("rId2");
InputSource sheetSource = new InputSource(sheet2);
parser.parse(sheetSource);
sheet2.close();
}
public void processAllSheets(String filename) throws Exception {
OPCPackage pkg = OPCPackage.open(filename);
XSSFReader r = new XSSFReader( pkg );
SharedStringsTable sst = r.getSharedStringsTable();
XMLReader parser = fetchSheetParser(sst);
Iterator<InputStream> sheets = r.getSheetsData();
while(sheets.hasNext()) {
System.out.println("Processing new sheet:\n");
InputStream sheet = sheets.next();
InputSource sheetSource = new InputSource(sheet);
parser.parse(sheetSource);
sheet.close();
System.out.println("");
}
}
public XMLReader fetchSheetParser(SharedStringsTable sst) throws SAXException, ParserConfigurationException {
XMLReader parser = SAXHelper.newXMLReader();
ContentHandler handler = new SheetHandler(sst);
parser.setContentHandler(handler);
return parser;
}
/**
* See org.xml.sax.helpers.DefaultHandler javadocs
*/
private static class SheetHandler extends DefaultHandler {
private SharedStringsTable sst;
private String lastContents;
private boolean nextIsString;
private SheetHandler(SharedStringsTable sst) {
this.sst = sst;
}
public void startElement(String uri, String localName, String name,
Attributes attributes) throws SAXException {
// c => cell
if(name.equals("c")) {
// Print the cell reference
System.out.print(attributes.getValue("r") + " - ");
// Figure out if the value is an index in the SST
String cellType = attributes.getValue("t");
if(cellType != null && cellType.equals("s")) {
nextIsString = true;
} else {
nextIsString = false;
}
}
// Clear contents cache
lastContents = "";
}
public void endElement(String uri, String localName, String name)
throws SAXException {
// Process the last contents as required.
// Do now, as characters() may be called more than once
if(nextIsString) {
int idx = Integer.parseInt(lastContents);
lastContents = sst.getItemAt(idx).getString();
nextIsString = false;
}
// v => contents of a cell
// Output after we've seen the string contents
if(name.equals("v")) {
System.out.println(lastContents);
}
}
public void characters(char[] ch, int start, int length) {
lastContents += new String(ch, start, length);
}
}
public static void main(String[] args) throws Exception {
ExampleEventUserModel example = new ExampleEventUserModel();
example.processOneSheet(args[0]);
example.processAllSheets(args[0]);
}
}
Can someone please explain to me how the Event API works? Is it the same as the event-based architecture or is it something else?
A *.xlsx file, which is Excel stored in Office Open XML and is what apache poi handles as XSSF, is a ZIP archive containing the data in XML files within a directory structure. So we can unzip the *.xlsx file and get the data directly from the XML files then.
There is /xl/sharedStrings.xml having all the string cell values in it. And there is /xl/workbook.xml describing the workbook structure. And there are /xl/worksheets/sheet1.xml, /xl/worksheets/sheet2.xml, ... which are storing the sheets' data. And there is /xl/styles.xml having the style settings for all cells in the sheets.
Per default while creating a XSSFWorkbook all those parts of the *.xlsx file will become object representations as XSSFWorkbook, XSSFSheet, XSSFRow, XSSFCell, ... and further objects of org.apache.poi.xssf.*.* in memory.
To get an impression of how memory consuming XSSFSheet, XSSFRow and XSSFCell are, a look into the sources will be good. Each of those objects contains multiple Lists and Maps as internally members and of course multiple methods too. Now imagine a sheet having hundreds of thousands of rows each containing up to hundreds of cells. Each of those rows and cells will be represented by a XSSFRow or a XSSFCell in memory. This cannot be an accusation to apache poi because those objects are necessary if working with those objects is needed. But if the need is really only getting the content out of the Excel sheet, then those objects are not all necessary. That's why the XSSF and SAX (Event API) approach.
So if the need is only reading data from sheets one could simply parsing the XML of all the /xl/worksheets/sheet[n].xml files without the need for creating memory consuming objects for each sheet and for each row and for each cell in those sheets.
Parsing XML in event based mode means that the code goes top down through the XML and has callback methods defined which get called if the code detects the start of an element, the end of an element or character content within an element. The appropriate callback methods then handle what to do on start, end or with character content of an element. So reading the XML file only means running top down through the file once, handle the events (start, end, character content of an element) and are able getting all needed content out of it. So memory consuming is reduced to storing the text data gotten from the XML.
XSSF and SAX (Event API) uses class SheetHandler which extends DefaultHandler for this.
But if we are already at this level where we get at the underlying XML data and process it, then we could go one more step back too. Native Java is able handling ZIP and parsing XML. So we would not even need additional libraries at all. See how read excel file having more than 100000 row in java? where I have shown this. My code uses Package javax.xml.stream which also provides using event based XMLEventReader but not using callbacks but linear code. Maybe this code is simpler to understand because it is all in one.
For detecting whether a number format is a date format, and so the formatted cell contains a date / time value, one single apache poi class org.apache.poi.ss.usermodel.DateUtil is used. This is done to simplify the code. Of course even this class we could have coded our self.
I'm beginning to learn the Stanford CoreNLP Java API, and am trying to print the syntax tree of a sentence. The syntax tree is supposed to be generated by the ParserAnnotator. In my code (posted below), the ParserAnnotator runs without errors but doesn't generate anything. The error only shows up when the code tries to get the label of the tree's root node, and the tree is revealed to be null. The components that run before it generate their annotations without any problems.
There was one other person on SO who had a problem with the ParserAnnotator, but the issue was with memory. I've increased the memory that I allow Eclipse to use, but the behavior is the same. Running the code in the debugger also did not yield any errors.
Some background information: The sentence I used was "This is a random sentence." I recently upgraded from Windows 8.1 to Windows 10.
public static void main(String[] args){
String sentence = "This is a random sentence.";
Annotation doc = initStanford(sentence);
Tree syntaxTree = doc.get(TreeAnnotation.class);
printTreePreorder(syntaxTree);
}
private static Annotation initStanford(String sentence){
StanfordCoreNLP pipeline = pipeline("tokenize, ssplit, parse");
Annotation document = new Annotation(sentence);
pipeline.annotate(document);
return document;
}
private static StanfordCoreNLP pipeline(String components){
Properties props = new Properties();
props.put("annotators", components);
return new StanfordCoreNLP(props);
}
public static void printTreePreorder(Tree tree){
System.out.println(tree.label());
for(int i = 0;i < tree.numChildren();i++){
printTreePreorder(tree.getChild(i));
}
}
You're trying to get the tree off of the document (Annotation), rather than the sentences (CoreMap). You can get the sentences with:
Tree tree = doc.get(SentencesAnnotation.class).get(0).get(TreeAnnotation.class)
I can also shamelessly plug the Simple CoreNLP API:
Tree tree = new Sentence("this is a sentence").parse()
Guys Im using the following custom code to load 20 images from resources and present in a viewpager
public class CustomPagerAdapter extends PagerAdapter {
int[] mResources = {
R.drawable.slide1,
R.drawable.slide2,
R.drawable.slide3,
R.drawable.slide4,
R.drawable.slide5,
R.drawable.slide6,
R.drawable.slide7,
R.drawable.slide8,
R.drawable.slide9,
R.drawable.slide10,
R.drawable.slide11,
R.drawable.slide12,
R.drawable.slide13,
R.drawable.slide14,
R.drawable.slide15,
R.drawable.slide16,
R.drawable.slide17,
R.drawable.slide18,
R.drawable.slide19,
R.drawable.slide20,
};
Context mContext;
LayoutInflater mLayoutInflater;
public CustomPagerAdapter(Context context) {
mContext = context;
mLayoutInflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
#Override
public int getCount() {
return mResources.length;
}
#Override
public boolean isViewFromObject(View view, Object object) {
return view == ((LinearLayout) object);
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
View itemView = mLayoutInflater.inflate(R.layout.pager_item, container, false);
ImageView imageView = (ImageView) itemView.findViewById(R.id.imageView);
imageView.setImageResource(mResources[position]);
container.addView(itemView);
return itemView;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
container.removeView((LinearLayout) object);
}
}
This works fine but I want to put the jpgs in a directory on the device so that they can be changed without recompiling the app
I think I need to get the images into the mResource array. I can get the path but not sure what format the code should be instead of using the draw-able lines
i have read articles on here but none make sense to me I am really new to this and the code looks nothing like the code I am using
can anyone point me in the right direction?
Any help is greatly appreciated
Mark
Yes, you can certainly do so. I will try to explain you the process step-by-step,
Step 1
Have a File object pointing to the path, like,
File directory = new File("path-to-directory");
Ensure that the path is to the directory with the images,
Step 2
List all the files inside the directory using listFiles() method, like
File[] allImages = directory.listFiles();
Now you have an array of all the files just like int[] mResources. The only difference being, now you have actual file references, while previously you had resource ids.
Step 3
You can just display the images in the ViewPager just like you did previously. But this is a bit tricky and can take you a considerable amount of time and code to get an image properly displayed from File.
You also need to take care of caching, so that when you load a previously loaded image again, it gets it from the cache.
To do all this, I recommend you to use this library (recommended by Google), Glide.
Setting an image is one line of code,
Glide.with(context).from(file).into(imageView);
That's it. Now you have your images displayed in a ViewPager from a directory in the device.
We are developing one application which will read multiple files & write multiple files i.e. one output file for one input file (name of output file must be same as input file).
MultiResourceItemReader can read multiple files but not simultaneously, which is a performance bottleneck for us. Spring batch provides multithreading support for this but again many threads will read the same file & try to write it. Since output file name must be same as Input file name, we can't use that option too.
Now I am looking for one more possibility, if I can create 'n' threads to read & write 'n' files. But I am not sure how to integrate this logic with Spring Batch framework.
Advance thanks for any help.
Since MultiResourceItemReader doesn't meet your performance needs you may take a closer look at parallel processing, which you already mentioned is a desirable option. I don't think many threads will read the same file and try to write it when running multi-threaded, if configured correctly.
Rather than taking the typical chunk-oriented approach you could create a tasklet-orient step that is partitioned (multi-threaded). The tasklet class would be the main driver, delegating calls to a reader and a writer.
The general flow would be something like this:
Retrieve the names of all the files that need to be read in/written out (via some service class) and save them to the execution context within an implementation of Partitioner.
public class filePartitioner implements Partitioner {
#Override
public Map<String, ExecutionContext> partition(int gridSize) {
Map<String, Path> filesToProcess = this.service.getFilesToProcess(directory); // this is just sudo-ish code but maybe you inject the directory you'll be targeting into this class
Map<String, ExecutionContext> execCtxs = new HashMap<>();
for(Entry<String, Path> entry : filesToProcess.entrySet()) {
ExecutionContext execCtx = new ExecutionContext();
execCtx.put("file", entry.getValue());
execCtxs.put(entry.getKey(), execCtx);
}
return execCtxs;
}
// injected
public void setServiceClass(ServiceClass service) {
this.service = service;
}
}
a. For the .getFilesToProcess() method you just need something that returns all of the files in the designated directory because you need to eventually know what is to be read and the name of the file that is to be written. Obviously there are several ways to go about this, such as...
public Map<String, Path> getFilesToProcess(String directory) {
Map<String, Path> filesToProcess = new HashMap<String, Path>();
File directoryFile = new File(directory); // where directory is where you intend to read from
this.generateFileList(filesToProcess, directoryFile, directory);
private void generateFileList(Map<String, Path> fileList, File node, String directory) {
// traverse directory and get files, adding to file list.
if(node.isFile()) {
String file = node.getAbsoluteFile().toString().substring(directory.length() + 1, node.toString().length());
fileList.put(file, directory);
}
if(node.isDirectory()) {
String[] files = node.list();
for(String filename : files) {
this.generateFileList(fileList, new File(node, filename), directory);
}
}
}
You'll need to create a tasklet, which will pull file names from the execution context and pass them to some injected class that will read in the file and write it out (custom ItemReaders and ItemWriters may be necessary).
The rest of the work would be in configuration, which should be fairly straight forward. It is in the configuration of the Partitioner where you can set your grid size, which could even be done dynamically using SpEL if you really intend to create n threads for n files. I would bet a fixed number of threads running across n files would show significant improvement in performance but you'll be able to determine that for yourself.
Hope this helps.
This is a bit involved, and I want to explain this succinctly without making you read a lot, then show the code. I'm not good at that.
Barebones explanation. In this assignment, we are learning, how to compile,interpret in comand prompt, create a package, create a class and sub-classes, import the sub-classes, and execute println commands in all the sub-classes as a single compiled program, and display such in command prompt. I'm missing something, and the subclass println commands don't display when I run GreetingsClass.java, the Superclass. They are all in the same package. The package directory is com.cisp2030.course, and the three Chapters class files exist in a .Chapters folder inside of .course.
First, GreetingsClass.java:
package com.cisp2030.course;
import com.cisp2030.course.Chapters.*;
public class GreetingsClass
{
Chapter1 c1 = new Chapter1();
Chapter2 c2 = new Chapter2();
Chapter3 c3 = new Chapter3();
public static void main(String[] args)
{
System.out.println("$ Greetings, CISP2030!");
System.out.println(c1);
}
}
This is supposed to import and instantiate the variables of the next code contained as Chapter1.class in .Chapters folder.
package com.cisp2030.course.Chapters;
public class Chapter1
{
public Chapter1()
{
System.out.println("Hello from Chapter1!");
}
}
Just imagine that the above code is one of three that range from Chapter1-Chapter3, and they have been compiled by Command Prompt into class files in their respective directory.
The expected output of compiling, interpreting, and running this program in command prompt should be one program which displays all 3-4 println commands. However, at this time, running hte command prompt only displays the one println command. I think this is because I need to sub-class the Chapter classes to GreetingsClass, and having them imported already, somehow direct GreetingsClass to execute the commands of hte Chapters class files, but I don't know how, and I've googled this consistently, and searched through my textbook and am none the wiser. I think I'm missing something in the code itself, but I don't know enough to come up with any ideas. Any help or advice would be greatly appreciated.
Code has been finished:
package com.cisp2030.course;
import com.cisp2030.course.Chapters.*;
public class GreetingsClass
{
public static void main(String[] args)
{
System.out.println("$ Greetings, CISP2030!");
Chapter1 c1 = new Chapter1();
Chapter2 c2 = new Chapter2();
Chapter3 c3 = new Chapter3();
}
}
Does that even compile?
Java doesn't allow static constructors.
public Chapter1() // removed "static"
{
System.out.println("Hello from Chapter1!");
}
c1 is a member of GreetingsClass. In main() you are in a static method, not a method of GreetingsClass and so you can't access it's members. Most obvious solution is to add GreetingsClass greetings = new GreetingsClass(); to main and try to get c1 out of that.