• Naming Conventions
• System.Out
• System.in
• Scanner Class
PROGRAM
Naming Conventions
• class name, interface name
– First Letter of each word must be in upper case and rest in lower case.
– e.g. String, StringBuffer, FileInputStream, ActionListener etc.
• method name, variable name
– First word in lower case
– For rest of words First Letter of each word must be in upper case and rest in lower case
– e.g. main(), print(), drawLine(), drawRoundRect() , toUpperCase( ) etc.
• package name
– should be in lowercase letter
– e.g. java, lang, sql, util etc.
• constants name
– should be in uppercase letter.
– Words separated by underscore
– e.g. RED, YELLOW, MAX_PRIORITY etc.
Program Input
Input to our java program can be provided by using different ways.
– Console Input (using System.in)
– GUI Interface
– Command Line Arguments
– Input Dialog Box
• System.out Object
• This object is attached to our
standard output device.
• This object is used to send data
to standard output device.
• It provides us methods print(),
println(), printf()..
etc to write
data into the object .
• System.in Object
• This object is attached to our
standard input device.
• This object is used to read data
from standard input device.0
• It provides us method read() to
read raw/binary data from the
object
System.in
We can not directly easily use this System.in
Object because it returns byte type of data.
i.e.
raw data
We have to wrap it in different objects to read
its data such as
– Scanner
– BufferedReader
– etc
Class Scanner – java.util
It is used to scan data from System.in Object.
Scanner Object can be created by using syntax:-
Scanner stdin=new Scanner(System.in);
methods:-
• String next()
– it returns the next token/word from the scanner.
• String nextLine()
– it returns the next line as a string.
• int nextInt()
– it scans the next token as an int value.
• long nextLong()
– it scans the next token as a long value. .
• float nextFloat()
– it scans the next token as a float value.
• double nextDouble()
– it scans the next token as a double value.
Program's
- WAP to read radius of
circle and find its area
and circumference.
package com.company;
import java.util.Scanner;
public class Easy
{
public static void main(String[] args)
{
Scanner likein=new Scanner(System.in);
System.out.print("Enter Radius ");
int r=likein.nextInt();
double a=3.14*r*r;
double c=2*3.14*r;
System.out.println("Area is "+a);
System.out.println("Circumference is "+c);
}
}
Output:-
Enter Radius
6
Area is 113.03999999999999
Circumference is 37.68
- WAP to read length and
breadth of rectangle and find
its area and perimeter.
package com.company;
import java.util.Scanner;
public class Easy
{
public static void main(String[] args) {
Scanner likein = new Scanner(System.in);
System.out.print("Enter Length and Breadth:");
int l = likein.nextInt();
int b = likein.nextInt();
int a = l * b;
int p = 2 * (l + b);
System.out.println("Area is " + a);
System.out.println("Perimeter is " + p);
}
}
Output:-
Enter Length and Breadth:
10 5
Area is 50
Perimeter is 30