Java tutorial- read input values from keyboard

Read input values from keyboard

System.in.read() method is used to read a single character from user’s input value. It will return numerical value of the input character. Therefore, you need to convert the value to the character using (char) conversion statement otherwise you may not understand what the user input.

Example:

public class Getcha
{
   public static void main(String[] args) throws Exception
   {
      char c;
      System.out.print("Enter a character:");
      c = (char)System.in.read();
      System.out.println("You entered " + c);
   }
}

In the sample above, exception must be thrown to pass the errors to the operating system to handle them. If exception is not thrown, your program will not be compiled.

Reading strings

There are many ways to read input strings value from user. However, in this tutorial, I introduce one way by using readLine() method. The readLine() method of BufferedReader class can be used to read input strings value from the user. To use this method, you must create BufferedReader object.

Example:

import java.io.*; // import IO package

public class ReadString
{
   public static void main(String[] args)throws IOException
   {
      String yourname;

      BufferedReader reader;//create BufferedReader object

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

      System.out.print(“Enter your name:”);

      yourname=reader.readLine(); 

     System.out.println(“Your name is ”+yourname);
         }
}

Type conversions

In Java programming language, you can convert from one type of data to another type by specifying that type in brackets ().

Example:

public class Conversion
{
   public static void main(String[] args)
   {
      int i;
      char c = 'a';
      i = (int)c; // The variable c with data type char is converted to integer type by using (int).
      i = 10;
      c = (char)i;
   }
}

In some circumstances, you need to convert a string value to an integer value. Because String  is not a simple data type but it is a class type, you cannot convert it as in the above example. Instead, you need to use Interger.parseInt() method of Integer class.

Example:

import java.io.*; // import IO package

public class ConvertString
{
   public static void main(String[] args)throws IOException
   {
      String valString;

      int val;

      BufferedReader reader;//create BufferedReader object

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

      System.out.print(“Enter your favorite number:”);

                 valString=reader.readLine(); 

            val=Integer.parseInt(valString); //string value is converted to integer value

System.out.println(“Your favorite number is ”+val);
         }
}