java-io

I am trying to delete a folder which has only files but no sub folders without success. Code: File rowFolder = new File(folderPath); String[] files = rowFolder.list(); for (String file : files){ File deleteFile = new File(file); System.out.println("deleting file -"+deleteFile.getName()); deleteFile.delete(); } System.out.println("deleting folder -"+rowFolder.getName()); rowFolder.delete(); Output: deleting file -testing.pdf deleting file -app_json.json deleting file -photo.jpg deleting folder -bundle_folder The code doesn't delete any folder nor any file. Why is that? You could be getting a

I'm a student practicing my File IO skills and I am coming up against a problem with reading Objects from a file using ObjectInputStream. The code is consistently throwing an InvalidClassException and I can't find how the code is throwing it online or by trial and error. Here's my code: import java.io.*; import java.util.ArrayList; import java.util.List; public class ReadFromFile { String filename; List<Object> os; public ReadFromFile(String filename) { this.filename = filename; os = new ArrayList<>(); } public Object[] readObject() { try { FileInputStream fis = new FileInputStream(filename);

Please show me the best/fast methods for: 1) Loading very small binary files into memory. For example icons; 2) Loading/reading very big binary files of size 512Mb+. Maybe i must use memory-mapped IO? 3) Your common choice when you do not want to think about size/speed but must do only thing: read all bytes into memory? Thank you!!! P.S. Sorry for maybe trivial question. Please do not close it;) P.S.2. Mirror of analog question for C#; For memory mapped files, java has a nio package: Memory Mapped Files Check out byte stream class for small files: Byte Stream Check out buffered I/O for larger

I work on Eclipse (Juno with JDK7), and the program runs (on Eclipse) fine. My problematic lines are: URL imageURL = new URL("http://www.idautomation.com/ocr-a-and-ocr-b-fonts/new_sizes_ocr.png"); RenderedImage img = ImageIO.read(imageURL); File outputfile = new File("saved.png"); ImageIO.write(img, "png", outputfile); But when i export the project to a jar file and try to run it via windows (7- 64 bit) command line, the following error appears: Exception in thread "main" java.lang.reflect.InvocationTargetException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect

I am working on the application which reads large amounts of data from a file. Basically, I have a huge file (around 1.5 - 2 gigs) containing different objects (~5 to 10 millions of them per file). I need to read all of them and put them to different maps in the app. The problem is that the app runs out of memory while reading the objects at some point. Only when I set it to use -Xmx4096m - it can handle the file. But if the file will be larger, it won't be able to do that anymore. Here's the code snippet: String sampleFileName = "sample.file"; FileInputStream fileInputStream = null;

In my online computer science class I have to write a program to determine the surface gravity on each planet in the solar system. I have gotten almost every aspect of it to work save one. I need to write the surface gravity to a file using a separate method. This is my current method: public static void writeResultsToFile(double g) throws IOException{ PrintWriter outFile = new PrintWriter(new File("planetaryData.txt")); outFile.printf("%.2f%n", g); outFile.close(); } My problem is that when I write it to a file it will overwrite the previous value. How do I get it include all of the values.