System Class - II

"System.out" meant for getting the output whereas System.in is standard input stream. This stream is to accept the input data from valid specified input device such as keyboard.

BufferedReader

BufferedReader Read text using character-input stream and then buffering the characters to provide for reading of characters. If size of buffer not specified then the default size is used. While using readLine(), it is necessay to throw an I/O Exception (input/out Exception). BufferedReader is part of java.io Library Package. 

An exception is an error that occurs within methods that creates an object that represents the same exception and thrown in the method which caused the error.

Example

import java.io.*;

    public class Buffer_Reader

        {

            public static void main(String args[])throws IOException

                {

                    BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

                    int Inum;

                    double Dnum;

                    String S;

                    System.out.print("Enter an Integer No.  ->  ");

                    Inum=Integer.parseInt(br.readLine());

                    System.out.print("Enter a Real No. ->  ");

                    Dnum=Double.parseDouble(br.readLine());

                    System.out.println("Integer No. "+Inum);

                    System.out.println("Real No. "+Dnum);

                }

            }

        

Scanner Class

Scanner is a simple text scanner which allows  primitive data types and strings. Scanner also breaks the  input into tokens using a delimiter, the default is space.

Unlike BufferedReader, Scanner never throw an unchecked exception. Although, the Scanner class give option to accept data from specified input device like keyboard and without handling exceptions. This may cause problem as it allows non integer data while using nextInt(). in particular Scanner never throw an IOException but a some of its constructors throw  FileNotFoundException which is a subclass of IOException. Java.util.Scanner, must be included to use Scanner Class.

Example

import java.util.*;

    public class ScanCl

        {

            public static void main(String args[])//throws IOException

                {

                    int N;

                    Scanner sc=new Scanner(System.in);

                    System.out.print("Enter a No : ");

                    N=sc.nextInt();

                    System.out.println("Number = "+N);

                }

        }

DataInputStream

The DataInputStream is also can use to read primitives and this too needs to throw I/O Exception. It may give an warning because InputStream class is the abstract class and an instance cannot be created of this class. DataInputStream is also from java.io Library Package and it is necessary to throw an I/O Exception. However, DataInputStream mainly used for reading from and  writing to a data file.

Example

import java.io.*;

    class DataInp

        {

            public static void main(String args[])throws IOException

                {

                    int a;

                    DataInputStream DS = new DataInputStream (System.in);

                    System.out.println("Enter a No. ");

                    a = DS.readInt();

                }

        }