8/10/2019 JOptionPane Class

1/19

JOptionPaneclass

8/10/2019 JOptionPane Class

2/19

DialogBoxes

Adialog

box

isasmallgraphicalwindowthatdisplaysamessagetotheuserorrequestsinput.

AvarietyofdialogboxescanbedisplayedusingtheJOptionPaneclass.

Twoofthedialogboxesare:

MessageDialog/ adialogboxthatdisplaysamessage.

InputDialog/ adialogboxthatpromptstheuserforinput.

8/10/2019 JOptionPane Class

3/19

UsingtheimportStatement

TheJOptionPaneclassisnotautomaticallyavailabletoyourJavaprograms.

Thefollowingstatementmustbebeforetheprogramsclassheader:

import javax.swing.JOptionPane;

Thisstatementtellsthecompiler

wheretofindtheJOptionPaneclass.

8/10/2019 JOptionPane Class

4/19

DialogBoxes

TheJOptionPaneclassprovidesstaticmethodstodisplayeachtypeofdialogbox.

8/10/2019 JOptionPane Class

5/19

MessageDialogs

JOptionPane.showMessageDialogmethodisusedtodisplayamessagedialog.

JOptionPane.showMessageDialog(null,"Hello World");

Thesecondargumentisthemessagethatistobe displayed

8/10/2019 JOptionPane Class

6/19

InputDialogs

Aninputdialogisaquickandsimplewaytoasktheusertoenterdata.

Thedialogdisplaysatextfield, an

OkbuttonandaCancelbutton. IfOkispressed, thedialogreturns

theusersinput.

IfCancelispressed, thedialogreturnsnull.

8/10/2019 JOptionPane Class

7/19

InputDialogs

String name;

name = JOptionPane.showInputDialog(

"Enter your name.");

Theargumentpassedtothemethodisthemessage

to

display

. IftheuserclicksontheOKbutton, namereferencesthestringenteredbytheuser.

IftheuserclicksontheCancelbutton, namereferencesnull.

8/10/2019 JOptionPane Class

8/19

NamesDialog.java

importjavax.swing.JOptionPane;publicclassNamesDialog

{ publicstaticvoidmain(String[]args) { StringfirstName; // Theuser'sfirstname StringmiddleName; // Theuser'smiddlename StringlastName; // Theuser'slastname // Gettheuser'sfirstname firstName=

JOptionPane.showInputDialog("Whatis" + "yourfirstname? ");

8/10/2019 JOptionPane Class

9/19

NamesDialog.java

// Gettheuser'smiddlename.

middleName=

JOptionPane.showInputDialog(

"Whatis" + "yourmiddlename?

");

// Gettheuser'slastname.

lastName=

JOptionPane.showInputDialog("Whatis"+ "yourlastname? ");

8/10/2019 JOptionPane Class

10/19

Example

// Displayagreeting

JOptionPane.showMessageDialog(n

ull, "Hello" + firstName+ " "+middleName+ " " + lastName);

System.exit(0);

}

}

8/10/2019 JOptionPane Class

11/19

TheSystem.exit() Method

AprogramthatusesJOptionPanedoesnotautomaticallystopexecutingwhentheendofthemain

methodisreached. Javageneratesathread, whichisa

processrunninginthecomputer,whenaJOptionPaneiscreated.

IftheSystem.exitmethodisnotcalled, thisthreadcontinuestoexecute.

8/10/2019 JOptionPane Class

12/19

TheSystem.exit() Method

TheSystem.exitmethodrequiresanintegerargument.System.exit(0);

Thisargumentisanexit

code

thatis

passedbacktotheoperatingsystem. Thiscodeisusuallyignored, however, it

canbeusedoutsidetheprogram: toindicatewhethertheprogramended

successfullyorastheresultofafailure.

Thevalue0 traditionallyindicatesthattheprogramendedsuccessfully.

8/10/2019 JOptionPane Class

13/19

ConvertingaStringtoa

Number

TheJOptionPanesshowInputDialogmethodalwaysreturnstheuser'sinputasaString

Stringcontaininganumber, suchas127.89, canbeconvertedtoanumericdatatype.

8/10/2019 JOptionPane Class

14/19

TheParseMethods

Parsemethodsconvertstringstonumericdatatypes

Theyare: Byte.parseByte Integer.parseInt Short.parseShort Long.parseLong Float

.parseFloat

Double.parseDouble

8/10/2019 JOptionPane Class

15/19

TheParseMethods/

Examples bytebVar= Byte.parseByte("1"); intiVar= Integer.parseInt("2599"); shortsVar= Short.parseShort("10"); longlVar= Long.parseLong("15908");

floatfVar= Float.parseFloat("12.3"); doubledVar=

Double.parseDouble("7945.6");

8/10/2019 JOptionPane Class

16/19

PayrollDialog.java

importjavax.swing.JOptionPane;

publicclassPayrollDialog

{

publicstaticvoidmain(String[]args) {

StringinputString; // Forreadinginput

Stringname; // Theuser'sname

inthours; // Thenumberofhoursworked

doublepayRate; // Theuser'shourlypayrate

doublegrossPay; // Theuser'sgrosspay

8/10/2019 JOptionPane Class

17/19

PayrollDialog.java

// Gettheuser'sname. name=

JOptionPane.showInputDialog("Whatis"+ "yourname?");

// Getthehoursworked. inputString= JOptionPane.showInputDialog(

"Howmanyhours +

didyouworkthisweek? "); // Converttheinputtoanint. hours= Integer.parseInt(inputString);

8/10/2019 JOptionPane Class

18/19

PayrollDialog.java

// Getthehourlypayrate.

inputString=

JOptionPane.showInputDialog("What

is+ " yourhourlypayrate? "); // Converttheinputtoadouble.

payRate=Double.parseDouble(inputString);

// Calculatethegrosspay. grossPay= hours* payRate;

8/10/2019 JOptionPane Class

19/19

PayrollDialog.java

// Displaytheresults.

JOptionPane.showMessageDialog(null,"Hello" + name+ ". Yourgrosspayis% "+ grossPay);

// Endtheprogram.

System.exit(0);

}}