InputOutput in Java

1
Input/Output in Java
2
Output

• To output to the command line, we use either
  System.out.print () or System.out.println() or
  System.out.printf()
• Examples using println
• System.out.println(One)
• System.out.println(Two)
• System.out.println(Buckle My Shoe)
• or
• System.out.println(One\nTwo\nBuckle My
  Shoe)

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Output Continued

• Examples using print println
• System.out.print(One )
• System.out.print(Two )
• System.out.print(Buckle my shoe)
• System.out.println()

4
Output Continued

• Examples using (the concatenate operator)
• int x 10, y 20
• System.out.println (x x \ny
• y \nx y (x y))
• What would be output if the parenthesis around x
  y were left off?

5
Using printf

• System.out.printf() is a method that receives
  multiple arguments.
• The first argument is a string that tells how to
  print the arguments that follow.
• Example s means print the argument as a string
• System.out.printf(s\ns\ns\n, One,
• Two, Buckle my shoe)

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printf continued

• int number1, number2, sum
• number110
• number130
• sum number1 number2
• System.out.printf(The sum of d d d,
  number1, number2, sum)

7
Command line Input

• The Scanner class is used for input from the
  command line.
• The Scanner class is in the package java.util so
  any program using the Scanner class must first
  include an import statement that is used to help
  the compiler locate the class.
• All import statements appear first in a java
  program before the class definition or any other
  statement (other than comments).

8

• import java.util.Scanner
• public class AddTwoNumbers
• public static void main(String str)
• int x, y
• //create a Scanner object to get input
• //System.in refers to standard input object
• Scanner input new Scanner(System.in)
• //Prompt for and read the first integer
• //using the Scanner objects nextInt method.
• //The program waits for the user to type in
• //an integer and press the ENTER key
• System.out.println(Enter the first
  integer)
• x input.nextInt()

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• System.out.println (Enter the next integer)
• y input.nextInt()
• sum x y
• System.out.println (Sum is d\n, sum)
• //end of main
• //end of class AddTwoNumbers

10
Displaying output using JOptionPane

• JOptionPane is a class in the package javax.swing
  that allows output to be displayed in a dialog
  box.
• Example
• JOptionPane.showMessageDialog(null,
• Welcome\nto\nJava)
• produces

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• String name
• JOptionPane.showInputDialog(
• What is your name?)
• String message
• Welcome, to Java Programming!
• name
• JOptionPane.showMessageDialog(null,
• message)