Java file i/o scanner

File Path Seems to be an issue here please make sure that file exists in the correct directory or give the absolute path to make sure that you are pointing to a correct file. Please log the file. You can change either one to match so that they line up, but just be sure they do. It may help to show the file extensions in whatever OS you're using. Also, for file location, it must be located in the working directory same level as the final executable the.

At first check the file address, it must be beside your. When you check this then try below. How are we doing? Please help us improve Stack Overflow. Take our short survey. Stack Overflow for Teams — Collaborate and share knowledge with a private group.

Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Reading a. Asked 9 years, 2 months ago. Active 2 years, 4 months ago. Viewed k times. I am getting the following error messages: java. File; import java. FileNotFoundException; import java. Ripon Al Wasim 35k 38 38 gold badges silver badges bronze badges. Try adding System. You do not open a.

I was able to find out my absolute path on mac. Add a comment. There are several potential error conditions that may occur when a program needs to get input from the user. If a user enters letters when a program is expecting numbers, an exception error will occur if the program assumes incorrectly that it has a valid integer to use in calculations. Programs must be written to survive bad input by the user.

One way to do this is to ensure that only valid input is accepted. Standard Java classes do not ensure that only valid input is accepted. They are designed to be very flexible to support the wide variety of input and output options available now and in the future.

This flexibility comes at the cost of increased complexity. The console window is the window that is automatically launched when you run a program from within Eclipse.

Console input is any input that is entered in the console window instead of typing it into a field or dialog box that pops up in a window. For example, when the nextLine method is called, the program waits for the user to enter information. Whatever the user types is returned to the program in the form of a String object. There are many ways to get information from the user. In many cases, the user must be told that they should enter some information. This is known as prompting the user.

A user prompt is a line of text that is output to the user that explains what information they should input next. We can prompt the user by displaying information in a dialog box, a program frame, or even the console window.

All programs that require the user to input information while the program is running must prompt the user for that information in some manner. When a program is waiting for input at the console, there is sometimes a blinking cursor in the console window indicating that the user should type some information. But, this is not always the case.

The user will only know what information to type if the program describes that information in the form of a user prompt. See Console Output for more information on user prompts. The java. But, you will need to learn about and use at least a couple of them. Either use the fully qualified name shown or import the specified package to use either of these classes. The Scanner class has a method called nextLine that returns a line of text as typed by the user.

There are two available constructors for creating a Scanner object. For console input, we will use the one that requires only one argument, an instance of an InputStream object. We will use the System. Subtle bugs are introduced into your program when you connect more than one Scanner object to the single InputStream object System. So, Java programmers create only one instance of the Scanner connected to System.

All keyboard operations will use that single shared Scanner object. The code below is placed with other class data members and is not inside any method. Did you remember to import the java. Scanner class? The Scanner class is not in the standard java. You must import the java. Scanner class to declare and create instances of the Scanner class. It's easiest to add the import java. Here's a complete program example that prompts the user for input and then repeats that data to the console window:.

Getting data from the user isn't so hard after all. But, it does require some additional work. There may be even more work to do, if you want to get an integer or other numeric value from the user. If the user types in "", that will be still be returned as a String object by the nextLine method of Scanner.

You will need to parse convert the String object into an int value if you wish to store it in an int variable or data member.

Here's one way to do this:. As you can see, the Scanner class contains a method named nextInt that returns the next input data available as an int value, that is, if the next input in the input stream is a valid integer format. If the next input is not a valid integer format, an InputMismatchException is thrown.

You may be wondering why are there two ways to read integers from the user. This flexibility allows you, the programmer, the option of which form is best for your program. The correct form to use depends upon what you wish to do with the rest of the line that remains after an integer is read from the current input line.

The first example should be used if the only thing available on the current input line is the integer value. The second example should be used if there are multiple data values to read on the same input line. The parseInt method declares that it may throw a NumberFormatException. If the user types any string of characters that can't be parsed into an int value, a NumberFormatException will be thrown and the program will crash.

Program often need to communicate with the outside world. The means of communication are input such as a keyboard and output such as the computer screen. Programs can also communicate through stored data, such as files. It is used to transfer data items in succession.

A stream can represent many different kinds of sources and destinations, including disk files, devices, other programs, and memory arrays. Streams support many different kinds of data, including simple bytes, primitive data types, localized characters, and objects. Some streams simply pass on data; others manipulate and transform the data in useful ways. No matter how they work internally, all streams present the same simple model to programs that use them: A stream is a sequence of data. Reading information into a program.

A program uses an input stream to read data from a source, one item at a time:. A program uses an output stream to write data to a destination, one item at time:. The data source and data destination pictured above can be anything that holds, generates, or consumes data. Obviously this includes disk files, but a source or destination can also another program, a peripheral device, a network socket, or an array.

Most of the classes implement sequential access streams. The sequential access streams can be divided into two groups: those that read and write bytes and those that read and write Unicode characters. Each sequential access stream has a speciality, such as reading from or writing to a file, filtering data as its read or written, or serializing an object. Types of Streams Byte Streams: Byte streams perform input and output of 8-bit bytes. They read and write data one byte at a time.

Other stream types are built on top of byte streams. Character Streams: All character stream classes are descended from Reader and Writer. We will look at two examples of writing programs using character streams, one that reads and writes one character at a time and one that reads and writes one line at a time.

For sample input, we'll use the example file xanadu.