java.util.scanner

I'm interested in using java.util.Scanner . I was reading the docs and saw a line saying A Scanner is not safe for multi threaded use without external synchronization. Can I confirm that this means that two separate Scanner objects in two separate threads operating on two separate files could interfere with each other? Can anyone help me to synchronise scanner object externally to use for safe thread operation? Terrible Tadpole If you use the same instance of Scanner in two threads you will have trouble unless you synchronise access to the object. But two separate instances of Scanner will

How to make scanner retry when exception occur? Consider this app running on CLI mode. Example: System.out.print("Define width: "); try { width = scanner.nextDouble(); } catch (Exception e) { System.err.println("That's not a number!"); //width = scanner.nextDouble(); // Wrong code, this bring error. } If the user not inputting double type input, then the error thrown. But i want after the error message appears. It's should be asking the user input the width again. How to do that? Pablo Francisco Pérez Hidalgo If I understood you correctly, you want the program to ask the user to re-enter a

I have an input text file in this format: <target1> : <dep1> <dep2> ... <target2> : <dep1> <dep2> ... ... And a method that takes two parameters function(target, dep); I need to get this parsing to call my method with each target and dep eg: function(target1, dep1); function(target1, dep2); function(target1, ...); function(target2, dep1); function(target2, dep2); function(target2, ...); What would be the most efficient way to call function(target,dep) on each line of a text file? I tried fooling around with the scanner and string.split but was unsuccessful. I'm stumped. Thanks. Read line into

I'm reading from a file that reads something like all on one line: Hello World!\nI've been trying to get this to work for a while now.\nFrustrating.\n And my Scanner reads that from the file and puts it in a String: Scanner input = new Scanner(new File(fileName)); String str = input.nextLine(); System.out.print(str); Now, I want the output then to be: Hello World! I've been trying to get this work for a while now. Frustrating. But instead I'm getting the exact same thing as the input. That is, each \n is included in the output and everything is on one line instead of separate lines. I thought

How can you search through a txt file for a String that the user inputs and then return that String to the console. I've written some code that doesn't work below, but I hope it can illustrate my point... public static void main(String[] args) { searchforName(); } private static void searchForName() throws FileNotFoundException { File file = new File("leaders.txt"); Scanner kb = new Scanner(System.in); Scanner input = new Scanner(file); System.out.println("Please enter the name you would like to search for: "); String name = kb.nextLine(); while(input.hasNextLine()) { System.out.println(input

In my current program one method asks the user to enter the description of a product as a String input. However, when I later attempt to print out this information, only the first word of the String shows. What could be the cause of this? My method is as follows: void setDescription(Product aProduct) { Scanner input = new Scanner(System.in); System.out.print("Describe the product: "); String productDescription = input.next(); aProduct.description = productDescription; } So if the user input is "Sparkling soda with orange flavor", the System.out.print will only yield "Sparkling". Any help will

In HACKERRANK this line of code occurs ery frequently. I think this is to skip whitespaces but what does that "\r\u2028\u2029\u0085" thing mean scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?"); Scanner.skip skips a input which matches the pattern, here the pattern is :- (\r\n|[\n\r\u2028\u2029\u0085])? ? matches exactly zero or one of the previous character. | Alternative [] Matches single character present in \r matches a carriage return \n newline \u2028 matches the character with index 2018 base 16(8232 base 10 or 20050 base 8) case sensitive \u2029 matches the character with index 2029

I am trying to read text from a text file. I need help figuring out when the end of file has occured. How can I determine this in Java? FileInputStream istream = new FileInputStream("\""+filename+"\""); Scanner input = new Scanner(istream); while(EOF != true) { .... } Thanks! You can check using hasNextLine() : Scanner input = new Scanner(new File("\""+filename+"\"")); while(input.hasNextLine()) { String data = input.nextLine(); } Thomas Langston Line based retrieval may be what you want, but token based can also be useful. You can see in documentation of Scanner public boolean hasNext()