Enter Strings and Integers in Java

JAVA ENTERING STRING:

A string is group of characters, alphabets, numbers enclosed within quotes.

Java provides a special mechanism for handling exceptions (exceptions means the wrong inputs which can cause the program to crash or fail). To handle exceptions is to append the clause “throws IOException” to the declaration of main() method as

Public static void main(Strings args[]) throws IOException

Following syntax should be followed to input string in java program:

Import java.io.*;

Public class hello

{

Public static void main(Strings args[])throws IOException

{

InputStreamReader reader= new InputStreamReader(System.in);

BufferedReader input= new BufferedReader(reader);

System.out.println(“Enter your name”);

String name=input.readLine();

System.out.println(“hello” +name+”!”);

}}

OUTPUT:

Enter your name Qamar Abbas

Hello Qamar Abbas

Explanation:

The program prints the prompt “Enter your name” and then waits for input. When user types “qmarabbas” and press enter, the system responses immediately and produces output on screen “ helloQamarabbas”

The whole scenario takes place in five steps or with five objects say system.in, reader, input, name, and system.out. System.in and system.out objects are defined in System Class. The other three are defined in the program on the ist, 2^nd and 3rd line.

Import Java.io.*: 

it tells the java compiler to check into the java input/output library for four classes as IOException,InputStreamReader, BufferdReader.

InputStreamReader reader:

Reader is an instance for the class InputStreamReader. The object reader will serve as a conduit (con-du-it), conveying data from the keyboard into the program. It reads the bytes that come from the keyboard such as {65 108 32 71 111 114 101 13}. These are the values of byte type.

BufferedReader input: 

Input is an instance for the class BufferedReader. It extracts the input in more convenient way. It converts the byte type input into character type {“Qamar Abbas”}. It uses its function readLine() to read a line of characters and assigns the string to the instance name of class String

String name=input.readLine():

the instance gets the value from the readline() function of called by input instance.

System.out.println(“hello” + name):

the system.out instance puts the stream of characters into its println() function which displays everything in parenthesis on screen.

Java Integer Input:

import java.io.*;

classneumaricinput{

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

InputStreamReader reader= new InputStreamReader(System.in);

BufferedReader input= new BufferedReader(reader);

String text=input.readLine();

System.out.println("Enter your age");

int age= new Integer(text).intValue();

System.out.println("you are "+age+" years old, now");

int year=2017-age;

System.out.println("so you proablly born in "+ year);

}

}

Everything is same as in string input method except following lines:

String text=input.readLine():

The method readline() called by input instance reads all the input in form of characters and assigns it to the instance of the String Class “text”.

Int age= new Integer(text).intValue():

This expression converts the character type input into integer type and stores it in the variable age.

Java Double Input

import java.io.*;

classAreaCircle{

public static void main(String args[])throws Exception{

InputStreamReader reader= new InputStreamReader(System.in);

BufferedReader input= new BufferedReader(reader);

System.out.println("Enter radius of circle");

String text= input.readLine();

Double x=new Double(text);

double r=x.parseDouble(text);

double area=Math.PI*r*r;

System.out.println("area of circle is "+area);

}

}

The structure of this program is same as previous two programs except the following lines;

Double x=new Double(text):

x is the object of the class Double. This x has obtained the value from text object of String class and this value cannot be used directly in expression because value in an object is different from the value in a variable.

Double r=x.parseDouble():

the value of object x from Double class is assigned to a double type integer r.

**for float use the line (float a=new Float(text).floatValue();)