I'm trying to rename the file that my program is outputting, but no matter what name i'm trying to change it to, it is stuck with the first name i listed which is "output.txt". I rename it to output1. txt and it still gives me output.txt could someone help with this?
public class Assignment2 {
public static void main(String[] args) {
if (args.length < 1) {
System.out.println("Sample command: java Assignment2 input.txt");
System.exit(0);
}
try {
Scanner scanner = new Scanner(new File(args[0]));
FileWriter fw = new FileWriter("output1.txt");
int i = 1;
while (scanner.hasNext()) {
System.out.println("Matrix #" + i);
processMatrix(scanner, fw);
i++;
System.out.println("");
fw.write(System.lineSeparator());
}
scanner.close();
fw.close();
} catch (FileNotFoundException ex) {
System.out.println(ex.getMessage());
} catch (IOException ex) {
Logger.getLogger(Assignment2.class.getName()).log(Level.SEVERE, null, ex);
}
}
From what I can see there is nothing wrong with your code.
So the only problem I can think of, is you are not building/compiling the file and therefore you are stuck on a older version of that file.
I don't know what technology stack you are using, but a still way to check this since its java, hopefully you got the environment variables configures. Just go to your terminal, to the file folder and:
javac Assignment2.java
java Assignment2
You can also tell me which IDE you are using, or how you are building/running your code.
Related
I'm trying to call a class whose part of the name is included in a string obtained by reading console input.
static void menu() {
System.out.println("Choose a menu:");
System.out.print("\n");
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String nome = null;
try {
nome = reader.readLine();
} catch (IOException e) {
e.printStackTrace();
}
System.out.print("\n");
System.out.println("Opening: " + nome);
System.out.print("\n");
String funzione = nome + ".funzione();";
try {
Runtime.getRuntime().exec(funzione);
} catch (IOException e) {
System.out.println(funzione);
e.printStackTrace();
}
Basically, if I write "print", I'd like to execute print.function(); which is called later in the program. The code works but it also outputs an error java.io.IOException: Cannot run program "print.function();": error=2, No such file or directory, yet print.function(); gets executed anyway.
To be clear, I am intentionally following this method rather than a switch case.
I think I'm executing the process in a wrong way, could anyone highlight me where? Many thanks.
I'm in a computer science (java) class right now and our task is to create a program that reads integers from an input.txt file (the professor will have this) and prints out all the integers into an output.txt file. Any exceptions/errors will need to be printed to an errors.txt file that our program creates. (We are learning about Exceptions in class now).
My program is able to read from an input file and print out just the integers to an output.txt, but I'm having problems printing out all the exceptions that might occur. For example, if the input file has "abc" as one of the lines, it should print out a message in the errors.txt file saying that it isn't an integer.
What happens with my program is that as soon as one exception is thrown, it doesn't keep going to print out all the other exceptions even if there are more to print. It just stops at that point.
So for example, something like this:
try{
while (fileScan.hasNext())
{
num = fileScan.nextInt();
}
}catch(Exception e)
{
erout.println(e); //prints the error to the file.
fileScan.nextLine();
}
erout is my PrintWriter object for the error.txt file. fileScan for the input.txt.
I'm just not sure how to get it to go through all of the input.txt file and keep track of all the exceptions it will throw, then print all those to an error.txt file. Any help would be appreciated, thanks. :)
You could move the while loop outside of the try statement.
while (fileScan.hasNext())
{
try{
num = fileScan.nextInt();
}catch(Exception e)
{
erout.println(e); //prints the error to the file.
fileScan.nextLine();
}
}
You need to re-order your while and try/catch:
List<Exception> exceptions = new ArrayList<>();
while (fileScan.hasNext()) {
try {
num = fileScan.nextInt();
// more code here to process num
} catch (Exception e) {
// Might also want to create a custom exception type to track
// The line/file that the error occurred upon.
exceptions.add(e);
fileScan.nextLine();
}
}
All you gotta do is move the try/catch within the while:
while (fileScan.hasNext())
{
try {
num = fileScan.nextInt();
}
catch (Exception e) {
erout.println(e); //prints the error to the file.
fileScan.nextLine();
}
}
I am building an optimization into a JPEG-Encoder written in Java. To do my benchmark i want to extract the orginal code and the optimized code into separated jars. Each jar has to take two arguments. The first on for the file name and the secound for the repeat of the compression of the jpeg.
public static void main(String[] args) {
String filepath = args[0];
try {
int times = Integer.getInteger(args[1]);
runBenchmark(filepath, times);
} catch(IOException | NumberFormatException ioe) {
System.out.println("Your arguments are Wrong! Use the follow order!");
System.out.println("1. Argument must be the filename of the image.");
System.out.println("2. Argument must be a number to repeat the compression.");
}
}
This is my main, witch handle my args. I cant run the arguments on IntellJ . Even if I compile it the a jar, i cant pass my arg2.
I passed two arguments via configuration in intellj and i get a NullPointerException. So i tried to figure out if my java can take two arguments. I wrote a simple main in vim and compiled ran it with two args and worked. I repeated this in a new Project in intellj.
This is working. But why?
You have to check if the parameter is a int or not.
Use Integer.parseInt() and a try-catch block to inform the user if a failure happen.
int times = 0;
try {
times = Integer.parseInt(args[1]);
} catch (Exception e) {
System.out.println("failure with a parameter");
}
I changed the method to Integer.parseInt(string) and now it works. It was the Integer.getInt() it . I thought i had now 2. arg because I get the NullPointerException.
Now it work with this code.
public static void main(String[] args) {
try {
String filepath = args[0];
int times = Integer.parseInt(args[1]);
runBenchmark(filepath, times);
} catch (NumberFormatException nfe) {
System.out.println("2. Arg must be an number");
} catch (IOException ioe) {
System.out.println("File not found.");
} catch(Exception e) {
System.out.println("Your arguments are Wrong! Use the follow order!");
System.out.println("1. Argument must be the filename of the image.");
System.out.println("2. Argument must be a number to repeat the compression.");
}
}
I have these 2 methods to read a number of integers from a file and insert them in a tree. It works fine if the file is found but if the file is not found it doesn't print "File not found". Why is it not going into the catch statement? Thanks!
public static void openF(Tree myT)
{
try
{
x=new Scanner(new File("Number.txt"));
readF(myT);
}
catch(Exception e)
{
System.out.println("File not found");
}
}
// to read from the file
public static void readF(Tree myT)
{
while(x.hasNext()) //keeps going till it reaches the end of file
{
int a =x.nextInt();
myT.insert(a); //insert in tree
}
}
I tested a simplified version of your code:
public static void main(String[] args) {
try {
new Scanner(new File("H:\\Hello.txt"));
System.out.println("The file exists.");
} catch (Exception e) {
System.out.println("File not found: " + e.getMessage());
}
}
When the file exists, it prints The file exists.. If not, it prints File not found: H:\Hello.txt (The system cannot find the file specified).
So no, the catch block is running as expected. The error is somewhere else in your code, but given that you're not providing the full code, nor a part which actually compiles (x is not declared), there is no way for us to guess where the actual error is.
I have the basics of my program finished.
The idea is that the user can specify a shape color width height etc. Upon inputting the data, constructors are called which create output, or there are other options which create output that the user can specify.
My goal is to get all of this output into a text file.
Currently I create a scanner for reading:
static Scanner input = new Scanner(System.in);
Then in my main driver method I create a Formatter:
public static void main(String[] args) {
Formatter output = null;
try{
output = new Formatter("output.txt");
}
catch(SecurityException e1){
System.err.println("You don't have" +
" write accress to this file");
System.exit(1);
}
catch(FileNotFoundException e){
System.err.println("Error opening or" +
" creating file.");
System.exit(1);
}
After each time I expect output I have placed this bit of code:
output.format("%s", input.nextLine());
And finally I close the file with
output.close()
The file is created but it is currently blank. I know I'm on the right track, because I've tried doing this:
output.format("%d", i);
where i is an integer of 0 and the file writes correctly.
However, I cannot seem to get it to work for an entire line, or for the output at all.
Please help!
I am not an expert but why can you not just use "FileWriter"?
Is it because you want to catch those exceptions to display useful information to the user?
Or have I misunderstood the question completely? - If so, sorry and just disregard this.
import java.io.FileWriter;
import java.io.IOException;
try
{
FileWriter fout = new FileWriter("output.txt"); // ("output.txt", true) for appending
fout.write(msg); // Assuming msg is already defined
fout.close();
}
catch (IOException e)
{
e.printStackTrace();
}