filewriter

问题 Is there anyway I can write to an already existing file using Filewriter For example when the user clicks a submit button: FileWriter writer = new FileWriter("myfile.csv"); writer.append("LastName"); writer.append(','); writer.append("FirstName"); writer.append('/n'); writer.append(LastNameTextField.getText()); writer.append(','); writer.append(FirstNameTextField.getText()); I want to be able to write new data into the already existing myfile.csv without having to recreate a brand new one

问题 This question already has answers here : Correct way to close nested streams and writers in Java [duplicate] (10 answers) Closed 4 years ago . Consider a BufferedReader as below: writer = new BufferedWriter(new FileWriter(new File("File.txt"), true)); In this case at the end of the application, I am closing the writer with writer.close() Will this be enough? Won't that FileWriter created with new FileWriter(new File("File.txt"), true) need to be closed? 回答1: It is not necessary to close it,

问题 I'm having trouble to append data to an existing file in HDFS. I want that if the file exists then append a line, if not, create a new file with the name given. Here's my method to write into HDFS. if (!file.exists(path)){ file.createNewFile(path); } FSDataOutputStream fileOutputStream = file.append(path); BufferedWriter br = new BufferedWriter(new OutputStreamWriter(fileOutputStream)); br.append("Content: " + content + "\n"); br.close(); Actually this method writes into HDFS and create a

问题 I'm having trouble to append data to an existing file in HDFS. I want that if the file exists then append a line, if not, create a new file with the name given. Here's my method to write into HDFS. if (!file.exists(path)){ file.createNewFile(path); } FSDataOutputStream fileOutputStream = file.append(path); BufferedWriter br = new BufferedWriter(new OutputStreamWriter(fileOutputStream)); br.append("Content: " + content + "\n"); br.close(); Actually this method writes into HDFS and create a

问题 I have an objectStore with hundreds of objects in it that I can view with code like this: db // already set by call to window.indexedDB.open .transaction(["mailing-list"]) .objectStore("mailing-list") .openCursor() .onsuccess = function (event) { var cursor = event.target.result; if (cursor) { console.log(cursor.value); cursor.continue(); } }; What I want to do is use a FileWriter to write out each object as it's retrieved; I don't want to accumulate all the objects in a giant array and write

问题 I have the following code to initialise a printwriter object-- /* This function is used to initialise the printwriter element so that it can begin the task of writing data into assignor.txt file... * */ public void startwriterassignor(String filename, boolean appendToFile) { //pw = null; try { if (appendToFile== true) { //If the file already exists, start writing at the end of it. pw = new PrintWriter(new FileWriter(filename, true)); } else { pw = new PrintWriter(new FileWriter(filename,

问题 I have a piece of code that generates new data whenever there is new data available as InputStream . The same file is overwritten everytime. Sometimes the file becomes 0 kb before it gets written. A webservice reads these files at regular intervals. I need to avoid the case when the file is 0 bytes. How do it do this? Will locks help in this case? If the browser comes in to read a file which is locked, will the browser continue to show old data from the cache until the lock is released and

问题 For some reason, when I create a new BufferedWriter and FileWriter in my program (Even if I haven't used it to write anything yet), it clears the file I have selected of all it's text. selectedFile is determined by a JFileChooser. public static File selectedFile; public static void Encrypt() throws Exception { try { //if I comment these two writers out the file is not cleared. FileWriter fw = new FileWriter(selectedFile.getAbsoluteFile()); BufferedWriter bw = new BufferedWriter(fw); List

问题 here is my Python code which I'm using to extract the Specific HTML from the Page links I'm sending as parameter. I'm using BeautifulSoup. This code works fine for sometimes and sometimes it is getting stuck! import urllib from bs4 import BeautifulSoup rawHtml = '' url = r'http://iasexamportal.com/civilservices/tag/voice-notes?page=' for i in range(1, 49): #iterate url and capture content sock = urllib.urlopen(url+ str(i)) html = sock.read() sock.close() rawHtml += html print i Here I'm

问题 How do I write over a specific line in a text file using FileWriter and PrintWriter? I don't want to have to make a new file every time. Edit: Can I just cycle through the file, get the length of the String at the indicated line number, and then use that length to backspace once I get to that line (to delete the String), and write in the new data? public static void setVariable(int lineNumber, String data) { try { // Creates FileWriter. Append is on. FileWriter fw = new FileWriter("data.txt",