Download week-3-lec-3ch02-inputoutput

Chapter 2: Java Fundamentals
Input and Output
statements
Standard Output Window

Using System.out, we can output multiple
lines of text to the standard output
window.
• The exact style of standard output window
depends on the Java tool you use.
The println Method

We use println instead of print to skip a line.
int x = 123, y = x + x;
System.out.println( "Hello, Dr. Caffeine.“ );
System.out.print( " x = “ );
System.out.println( x );
System.out.print( " x + x = “ );
System.out.println( y );
System.out.println( " THE END“ );
Commonly Used
Escape Sequences
4
Commonly Used
Escape Sequences

Example
System.out.println(“The string \”sunny\” contains five character”);
The string “sunny” contains five characters
Formatting Output with printf
System.out.printf("Hello there!");
Consists of only the format string and the statement:
System.out.printf("There are %.2f inches in %d
centimeters.%n",
centimeters / 2.54, centimeters);




Consists of both the format string and argumentList.
%.2f and %d are called format specifiers.
By default, there is a one-to-one correspondence between format
specifiers and the arguments in argumentList.
The first format specifier, %.2f, is matched with the first argument,
which is the expression centimeters / 2.54.
6
Formatting Output with printf





The second format specifier, %d, is matched with the
second argument, which is centimeters.
The format specifier %n positions the insertion point at
the beginning of the next line.
If centimeters = 150  150/2.54 =59.05511811023
The o/p would be :
There are 59.06 inches in 150 centimeters
The output of a printf statement is right-justified by
default. To force the output to be left-justified,
negative column widths may be used.
7
Example1
public class Example3_6
{
public static void main (String[] args)
{
int num = 763;
double x = 658.75;
String str = "Java Program.";
System.out.println("123456789012345678901234567890");
System.out.printf ( "%5d%7.2f%15s%n", num, x, str);
System.out.printf ("%15s%6d%9.2f %n",
str, num, x);
}
}
8
Example1
9
Example2
public class Example3_7
{
public static void main (String[] args)
{
int num = 763;
double x = 658.75;
String str = "Java Program.";
System.out.println("123456789012345678901234567890");
System.out.printf("%-5d%-7.2f%-15s ***%n", num, x, str);
System.out.printf("%-15s%-6d%-9.2f ***%n", str, num, x);
}
}
10
Example2
11
Formatting Output with printf
12
Standard Input


To input primitive data values, we use the
Scanner class.
4 steps are needed to be able to use input
primitive:

Step 1: import the Scanner class:


Step 2 : declaring a reference variable of a Scanner


Scanner read ;
//we named the object read
Step 3: creating an instance of the Scanner


import Java.util.Scanner;
read = new Scanner (System.in);
Step 4: use specific methods to enter data

int x = read.nextInt();
Example
1 import Java.util.Scanner;
2 Scanner input ; // declaring the reference variable of a Scanner
3 int area ,length, width; // declaring variables to store entries
4 input = new Scanner (System.in); // creating an instance
5 length = input.nextInt(); //reading the length from the keyboard
6 width = input.nextInt(); //reading the width from the keyboard
7 area = length * width ;
// computing the area
// displaying the result
8 System.out.println(“the legnth is ”+ lenght);
9 System.out.println(“the width is ”+ width);
10 System.out.println(“the area is ”+ area);
Common Scanner Methods

Method
Example
Scanner input = new Scanner (System.in);
nextByte( )
byte b = input.nextByte( );
nextDouble( )
double d = input.nextDouble( );
nextFloat( )
float f = input.nextFloat( );
nextInt( )
int i = input.nextInt( );
nextLong( )
long l = input.nextLong( );
nextShort( )
short s = input.nextShort( );
next()
String str = input.next();
Input

Reading a Single Character
if ch is a char variable. To input A into
ch, you can use the following statement:
ch = console.next().charAt(0);
16