How to Use System.in in Java
At times you might need to read console input provided by the user from the keyboard. The
System.in field permits you to read input from the keyboard. The input can be converted into a stream of characters and then buffered so that all characters up to but not including the Enter key can be presented to the program. To learn how to use
System.in in Java, follow these four steps.
- Open your text editor and type in the following Java statements:The program creates an
System.inas the constructor parameter.
System.inprovides the input stream from the keyboard and
InputStreamReaderreads the stream. Next, a
BufferedReaderobject is instantiated with the
InputStreamReaderobject passed to the constructor. The
BufferedReaderobject will buffer the input so that a line of text provided by the user is available to the program. The line of input is read using the
readLinemethod. This method can potentially throw the checked exception
IOException, so the method call must be in a try catch block.
- Save your file as UseSystemIn.java.
- Open a command prompt and navigate to the directory containing your Java program. Then type in the command to compile the source and hit Enter.
- Type in the command to run your program and hit Enter.At the prompt you can type your name and then hit Enter. The
readLineprovides the string data to the program. The program then displays your name, and this action verifies that the data was transferred to your program successfully.