Input and output in java

Input and Output (IO) are mainly used concepts in java real time applications to share objects from one place to another. Input represents data given to a program and output represents data displayed as a result of program. We are already familiar with the following two statements to display the output.

1
2
System.out.print();
System.out.println();

                Both of the statements are used to show the output on the screen. The difference between these two is that print() method keeps cursor in the same line after displaying the output and println() throws cursor to the next line after displaying the result.

Example to show the differences between print() and println() methods:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
public class Sysout{
      public static void main(String[] args){
             int a,b;
             a = 10;
             b = 15;
             c = a+b;
             System.out.print("result of a+b is ");
             System.out.println(c)
      }
}

          There are two output print statements in the above program. First print statement will print 'result of a+b is' and cursor will be in same line only. So, when next print statement will get executed that will print the value of c in same line only, means the complete output will print in same line only.
          When it will get executes the println() method , out put will print and cursor move to next line.

Accepting input from the keyboard:
          A Stream is required to accept data from the keyboard. Stream represents the data flow from one place to other place. It is like water-pipe where water flows. A Stream is always required if we want to move data from one place to other place.

          Basically there are two types of streams one is input stream and another one is output stream. Input streams which receive or read data coming from some other place. Output streams are those streams which send or write data from other place.
            • System.in : This represents Input Stream object, which by default represents standard input device, i.e.keyboard.
            • System.out : This represents Print Stream object, which by default represents standard output device, i.e. monitor.
            • System.err : This field also represents Print Stream object, which by default represents monitor.
          * Connect the keyboard to an input stream object. Here, we can use InputStreamReader that can read data from keyboard.

1
InputStreamReader reader = new InputStreamReader(System.in);
         
          In this statement, we are creating InputStreamReader object and connecting the keyboard (System.in) to it.

          * Connecting InputStreamReader to BufferedReader, which is another input type of stream. We are using BufferedReader as it has got methods to read data properly, coming from the stream.
1
BufferedReader br = new BufferedReader(reader);

          Here, we are creating BufferedReader object and connecting the InputStreamReader object to it.

Note: In the above two statements will combine and write in a single statement as,
1
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

          Now, we can read the data coming from the keyboard using read() and readLine() methods available in BufferedRerader class.
Accepting single character from the Keyboard:
          Follow these steps in order to accept single character from the keyboard.
              •  Create a BufferedReader class object(br).
              •  read a single character from the keyboard using read() method.

1
char ch = br.read();
         
          The above read() method it get ASCII number of the character in Integer format. That integer value can't save into character type variable char variable.

1
char ch = (char)br.read();
         
To accept and display a character from the keyboard:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
import java.io.*;

class Accept{
     public static void main(String[] args)throws IOException{
          /*create BufferedReader object to accept data from the keyboard*/
          BufferedReader br = new BufferedReader(new  InputStreamReader(System.in));
          //Ask for character to read it
          System.out.print("Enter a character: ");
          char ch = (char)br.read();

          //Display the character
          System.out.println("You entered: "+ch);
     }
}

Accepting a String from keyboard:
          For reading a String from keyboard there is a readLine() method in BufferedReader class.

1
String str = br.readLine();
         
          The below one is the example to read a String from the keyboard.

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
Import java.io.*;

public class Accept{
     public static void main(String[] args)throws IOException{
          /*Create BufferedReader object to accept data from keyboard*/
          BufferedReader br = new BufferedReader(new   InputStreamReader(System.in));

          //Ask for String and read it
          System.out.println("Enter a name: ");
          String name = br.readLine();
         
          //Display the String
          System.out.println("You entered: "+name);
     }
}

Accepting an Integer value from the keyboard:
          First we should accept the integer number from the keyboard as a String, using readLine().

1
String str = br.readLine();
         
          The number is in str in String format. That should be converted into int by using parseInt() method of Integer class.

1
int n = Integer.parseInt(str);

          The above two statements combined into a single statement.

1
int n = Integer.parseInt(br.readLine());
         
Here, is the example to read int value from the keyboard,

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
import java.io.*;

public class AcceptInt{
     public static void main(String[] args){
          /* Create BufferedReader object to read data from keyboard */
          BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
          //Ask for integer and read it
          System.out.println("Enter an int value:");
          int num = Integer.parseInt(br.readLine());

          //display the int
          System.out.println("you entered:"+num);
     }
}

Reading input from Scanner:
          java.util.Scanner class will be helpful to read input from the keyboard or from a text file. When Scanner class loads input, that breakes into peaces called 'tokens'. These tokens can be retrieved from the Scanner object using the following methods.
            • next() - to read String
      • nextByte() - to read byte value
      • nextInt() - to read an Integer value
      • nextFloat() - to read float value
      • nextLong() - to read long value
      • nextDouble() - to read double value

          To read input from the keyboard we will use Scanner class as below

1
Scanner sc = new Scanner(System.in);

          If the user has given an integer value from the keyboard, it is stored into the Scanner object as a token. We can use the method sc.nextInt().
          Here is the program to read input from the keyboard.

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
package com.javatbrains.io;

import java.util.Scanner;

public class ScannerKeyboard {
     public static void main(String[] args) {
          System.out.println("Enter id name sal:");
          Scanner sc = new Scanner(System.in);

          int id = sc.nextInt();
          String name = sc.next();
          float sal = sc.nextFloat();

          System.out.println("Id =  " + id);
          System.out.println("Name = " + name);
          System.out.println("Salary = " + sal);
     }
}
OutPut:
     Enter id name sal:
          12 JavaTBrains 1234.23  //passing input
          Id =  12
          Name = JavaTBrains
          Salary = 1234.23

          Here is the example to read text file using Scanner class. You need to create one text file with some content and pass that file path into File. This will read each and every line in the file and will print in console also as of the file format.

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
package com.javatbrains.io;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class ScannerFile {
     public static void main(String[] args) throws FileNotFoundException {
          File file = new File("C:/<Your File Name>.txt");
          Scanner sc = new Scanner(file);

          int lineNumber = 1;
          while (sc.hasNextLine()) {
              String text = sc.nextLine();
              System.out.println(text);
              lineNumber++;
          }
     }
}

          If your passing input file is not present in the path, it will throws an exception called  FileNotFoundException.

Do you know?
Location: India

Comments

Post a Comment

Popular posts from this blog

Hibernate auto increment with example

In previous example we learn how to map java object with database table for manually(not using auto increment) assigned all the values.  To create primary key auto increment application by using hibernate mapping(hbm.xml) or using annotations continue reading this article.  W e need to create a database and create an employee table by using the below query. Table: CREATE table EMPLOYEE( eid integer ( 10 ) primary key not null , firstname varchar ( 30 ), lastname varchar ( 30 ), designation varchar ( 30 ), salary double( 10 , 2 )); Here, we will create a bean/POJO (Plain Old Java Object) class of employee. Employee.java: package com . javatbrains . hibernate ; import java.io.Serializable ; /*This is the POJO class. It contains only Getter and Setter methods*/ public class Employee implements Serializable { private static final long serialVersionUID = - 75885815725314443L ; private int eid ; ...
Read more

how to count the page views by using JSP

To count no.of page's are viewed by user in your application is a challenge in real time application. In this page we will see how to count the page views when user has viewed the page.           Here, we will do one example how many times user has visited each page in our application. In this post we will come to know, how to count the total application page views as well as individually each pages count.           Let us assume my web application name is "Page Counter". For creating the web application in eclipse IDE, Click here . This Page Counter contains three pages, assume that are the different pages in an application. But, there is the link between each other files for navigating from one page to another. Also it will show the total pages view count and individual page view count in all the pages. Let us see, below is my first jsp file,         ...
Read more

Multithreading in java with example

Multithreading  is one of the most important concept in core java. In this article we will learn what is multithreading? , what is the use of it? and What is the use of Synchronization and when to use it?  with detailed examples. At a time, two or more threads are accessing the same object is called as Multithreading  in Java .  First, we will create two threads for two objects. It is also possible to run two or more threads on a single class object. In this case, there is a possibility to get unreliable results. If the two threads are perform same task, then they need same object to be executed each time. For your better understanding, take an example of any reservations like, railway, movie ticket booking,etc. Let us think only one berth is available in a train and two passengers are asking for that berth. The first person has sent a request to allocate that ticket/berth to him. At the same time, the second person also sent a request to allocate that ...
Read more

How to retrieve data from table by using JDBC with example

To retrieve data from mysql data table by using jdbc, we need to confirm weather which table data we need to retrieve. To confirm open your mysql and view all database names by using the ' show databases ' commands in mysql. Then select which is your database name from showing list of database names, by using the ' use <database name> ' command in mysql. Then we need to see all your existing tables by executing the ' show tables ' command. This command gives you the list of existing tables in your selected database. You need to use existing table only you can follow with that. But, here we will see with entirely new which is not existing in mysql database. Now, We will create simple mysql table with minimal columns. create table emp(eno integer(10), ename varchar(30), sal float); The above command creates a new table, we will move further to insert records into emp table by executing the insert which we mentioned in the below. ...
Read more

Prime, Fibonacci and Factorial number with example in java

Prime number, Fibonacci series and Factorial number programs are most commonly asked questions in interview. Read this article to know what is and how to write programs for prime number, fibonacci series and factorial number. Prime Number: prime number is natural number greater than 1 that has no positive divisor other than 1 and itself. A natural number greater than 1 is not a prime number, is called Composite number . For example, 7 is a prime number. Because it can divide with 1 and 7 only. Where as 8 is composite number. Since it has the divisor 2 and 4 in addition to the 1 and 8. The below example represents the finding the passing number is prime number or not. If the passing number is prime number it will print true otherwise it will print false. package com . javatbrains . practice ; public class PrimeNumber { public boolean isPrimeNumber ( int number ) { if ( number <= 1 ) return false ; // There's only one ...
Read more

How to insert images into database using JDBC?

How to insert images into database table by using JDBC? To know about these topic follow the below lines,           Before going to write a JDBC program for inserting images into database table, we need to create a specific table for inserting images column datatype. For creating the database table, execute the below command in MySQL command prompt. 1 2 3 4 CREATE TABLE ` images ` ( ` image_id ` int ( 11 ) NOT NULL AUTO_INCREMENT, ` image_flag ` int ( 11 ) NOT NULL , ` image ` longblob NOT NULL , PRIMARY KEY ( ` image_id ` ));           After executing the above query in MySQL command prompt, execute the below query to know weather the above table query is created or not. 1 Show tables;            When you have executed the above query that will show you the list of table which all exists in the current database. Current tab...
Read more

How to sort list of objects in java with examples

We could achieve list of objects sorting in java by using sort() method which is available under Collections class as well as by using Comparable and Comparator  interfaces. Comparable and Comparator are two interfaces in java used to sort list of objects. These interfaces are available under java.util package along with Collections  class and other classes and interfaces. Comparable interface contains the method of       public int compareTo(Object obj) Comparator interface contains the method of       public int compare(Object obj1, Object obj2) The compare() and compareTo() methods will return negative integer(-1), or zero(0) or positive integer(1). When the first obj1 is less than obj2 method will return negative integer. When obj1 is equals to obj2 will return zero and when obj1 is grater than obj2 it will return positive integer. If it's objects are stored in any Collection classes like ArrayList, H...
Read more

String interview questions and answers

String interview questions and answers are placed the current post as of my experience in interviews. This will helps who are trying to attend interview as fresher as well as experience. If any one is facing any other questions which are not present in the current page, please drop me an email to " subbareddynallamachu@gmail.com ".  Q1:  String is a class or data type? A: String is a class in java.lang package. But, in java, all classes are also are considered as data types. So we can take String as data type also. Q2:  What is the difference between == and equals() methods in java? A: == operator compares the references of the String object. It does not compare the content of the object. equals() method compares the contents. While comparing the Strings, equals method should be used as it yields the correct result. Q3:  What is String constant pool? A: String constant pool is a separate block of memory where the String objects are held by JVM....
Read more

Exception in thread "main" java.lang.NoClassDefFoundError: javax/transaction/SystemException

Exception in thread "main" java.lang.NoClassDefFoundError: javax/transaction/SystemException error we got in Hibernate 4.3 to work with my MySQL database. We are using hibernate code generation tool in Eclipse and we are able to connect to the database using the Hibernate configuration file. When we try to run code in my Main class application is connecting to the database, but transaction is failing and we got the following error: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Exception in thread "main" java . lang . NoClassDefFoundError : javax / transaction / SystemException at java . lang . Class . forName0 ( Native Method ) at java . lang . Class . forName ( Unknown Source ) at org . jboss . logging . Logger . getMessageLogger ( Logger . java : 2248 ) at org . jboss . logging . Logger . getMessageLogger ( Logger . java : 2214 ) at org . hibernate . cfg . Configuration .< clinit >( Configuration . java : 184 ) at be . comp . permanenti...
Read more

Store file into table by using JDBC with example

To store large data files or text files into database table, we will use CLOB (Charecter Large Object) datatype of SQL . By using CLOB it is possible to save entire text book or a file or resume into a column of data table. If your using MySQL database instead of CLOB use LONGTEXT to save file into datatable. For saving files into a data table, we need to create one table which will contains a column type as CLOB to store files. Here, is the query to create a data table. 1 2 3 4 create table myfiles( file_id int ( 10 ), file_name varchar ( 30 ), file_type LONGTEXT); Once table creation completes, these table contains the 3 columns one is file_id represents the file id, file_name represents the name of the file and finally file_type will get save entire file into the table column. Now, we will move to write a JDBC program which will saves the file into the newly creating table. Here is the JDBC program, 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16...
Read more