jedi- how to get input in java

8/12/2019 Jedi- how to get input in java

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Introduction to Programming 1 1

5 Getting Input fromKeyboard


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Objectives

At the end of the lesson, the student should be able to:

Create an interactive Java program that gets input from the

keyboard Use the BufferedReader class to get input from the

keyboard using a console

Use the JOptionane class to get input from the keyboard

using a graphical user interface


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Getting Input from the

Keyboard !"o methods of getting input:

BufferedReader class

JOptionane class

graphical user interface


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Using BufferedReader Class

BufferedReader class

#ound in the $ava%io package

Used to get input


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teps to get Input&% Add this at the top of your code:

import java.io.*;

'% Add this statement:

BufferedReader dataIn = new BufferedReader( newInputStreamReader( System.in) );


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teps to get Input(% )eclare a temporary *tring variable to get the input, and

invoke the read+ine- method to get input from thekeyboard% .ou have to type it inside a try/catch block%

try{

String temp = dataIn.readLine();

}catch( IOException e ){System.out.println(Error in getting input);

}


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ample !rogram1 import java.io.BufferedReader;

2 import java.io.InputStreamReader;

3 import java.io.IOException;

4

5 public class GetInputFromKeyboard {

6

7 public static void main( String[] args ){

8 BufferedReader dataIn = new BufferedReader(new9 InputStreamReader( System.in) );

10

11 String name = "";

12 System.out.print("Please Enter Your Name:");

13 try{

14 name = dataIn.readLine();

15 }catch( IOException e ){16 System.out.println("Error!");

17 }

18 System.out.println("Hello " + name +"!");

19 }

20 }


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ample !rogram

import java.io.BufferedReader;import java.io.InputStreamReader;

import java.io.IOException;

!he lines,

indicate that "e "ant to use the classes BufferedReader,0nput*treamReaderand 0O12ception"hich are inside the$ava%iopackage%

!hese statements can also be "ritten as,

import java.io.*;


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ample !rogram

!he Java Application rogramming 0nterface A0- containshundreds of predefined classes that you can use in yourprograms% !hese classes are organi3ed into "hat "e callpackages%

ackagescontain classes that have related purpose%


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ample !rogram

public class GetInputFromKeyboard {

public static void main( String[] args ){

!he statement,

means "e declare a class named 4et0nput#rom5eyboard

!he ne2t statement declares the main method%


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ample !rogram

BufferedReader dataIn = new BufferedReader(new InputStreamReader

( System.in) );

!he statement,

declares a variable named dataIn, "ith the class typeBufferedReader%

)on6t "orry about "hat the synta2 means for no"% 7e "ill cover more aboutclasses and declaring classes later in the course%


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ample !rogram

String name = "";

System.out.print("Please Enter Your Name:");

!he statement,

declares a Stringvariable "ith identifier name.

!he ne2t statement,

outputs a *tring on the screen asking for the user6s name


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ample !rogram

try{

name = dataIn.readLine();

}catch( IOException e ){

System.out.println("Error!");

}

!he given block defines a try/catch block%

!his assures that the possible e2ceptions that could occur inthe statement


"ill be catched%

7e "ill cover more about e2ception handling in the latter part of thiscourse%


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ample !rogram

8o" going back to the statement,

the method call, data0n%read+ine-, gets input from the user

and "ill return a *tring value%

!his value "ill then be saved to our namevariable, "hich "e"ill use in our final statement to greet the user,


System.out.println("Hello " + name + "!");


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Using "option!ane Class

Another "ay to get input from the user is by using theJOptionane class "hich is found in the $ava2%s"ingpackage%

JOptionane makes it easy to pop up a standard dialog bo2that prompts users for a value or informs them of something%


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ample !rogram1 import javax.swing.JOptionPane;

2

3 public class GetInputFromKeyboard {

4

5 public static void main( String[] args ){

6 String name = "";

7 name=JoptionPane.showInputDialog(Please enter your name");

8 String msg = "Hello " + name + "!";9 JOptionPane.showMessageDialog(null, msg);

10 }

11}


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ample !rogram Output


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ample !rogram

import javax.swing.JOptionPane;

!he statement,

indicates that "e "ant to import the class JOptionane fromthe $ava2%s"ing package%

!his can also "ritten as,import javax.swing.*;


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ample !rogram

name=JoptionPane.showInputDialog(Please enter your name");

!he statement,

creates a JOptionane input dialog, "hich "ill display adialog "ith a message, a te2tfield and an O5 button as

sho"n in the figure% !his returns a *tring "hich "e "ill save in the name

variable%


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ample !rogram

String msg = "Hello " + name + "!";

!he statement,

creates the "elcome message, "hich "e "ill store in the

msgvariable%


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ample !rogram

JOptionPane.showMessageDialog(null, msg);

!he statement,

displays a dialog "hich contains a message and an O5

button%


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ummary

)iscussed t"o "ays of getting input from the user by usingthe classes:

BufferedReader

JOptionane

Brief overvie" of packages

4roups related classes in Java

Classes inside packages can be used by importing the package

jedi- how to get input in java

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