Working with Date

ISYS 350

Date Class, java.util.Date • The class Date represents a specific instant in time, represents

the number of milliseconds that have passed since January 1, 1970 00:00:00.000. – For a date before 1/1/1970, it is a negative number

• Constructor without argument: Current date– Date myDate = new Date();– System.out.println("Today is: " + myDate.toString());

• Constructor without argument: – Date(long date)

Constructs a Date object using the given milliseconds time value.– It is basically impossible to know precisely how many milliseconds

• GetTime method: Returns the number of milliseconds since January 1, 1970, 00:00:00 GMT represented by this Date.

• Note: import java.util.Date;

GregorianCalendar Class

• It has a constructor that lets user to specify a specific date:– GregorianCalendar ThisDate = new

GregorianCalendar(2009,Calendar.SEPTEMBER,10);

• Has fields to get info about date:– YEAR, MONTH,DAY_OF_MONTH , DAY_OF_WEEK,

WEEK_OF_MONTH, DAY_OF_WEEK_IN_MONTH, AM_PM, HOUR, HOUR_OF_DAY, etc.

– System.out.println("Year: " + ThisDate.get(Calendar.YEAR));

GregorianCalendar’s GetTime method

• public final Date getTime() – Returns a Date object representing this Calendar's

date.– This is different from the Date class getTime

method.

• Note: We can use GregorianCalendar object to create a date; then use its getTime method to create a Date object.

Compute Days to Christmas

Date toDay = new Date();GregorianCalendar ThisDate = new GregorianCalendar(2009,Calendar.DECEMBER,25);Date ChristMas=ThisDate.getTime();double datediff= (ChristMas.getTime()-toDay.getTime())/(24*60*60*1000);System.out.println("days to Christmas: " + datediff);

Compute Age from Birthday

Date toDay = new Date();GregorianCalendar BirthDay = new GregorianCalendar(1990,Calendar.DECEMBER,25); Date DoB=BirthDay.getTime(); double Age= (toDay.getTime()-DoB.getTime())/(24*60*60*1000)/365.25; System.out.println("Age: " + Age);

GregorianCalendar TodayDate= new GregorianCalendar();GregorianCalendar BirthDay = new GregorianCalendar(1990,Calendar.DECEMBER,25);Age= TodayDate.get(Calendar.YEAR) - BirthDay.get(Calendar.YEAR);System.out.println("Age: " + Age);

Method 1: Using Date object’s GetTime method:

Method 2: Using GregorianCalendar’s YEAR property

Working with String

String Class Methods• toLowerCase()• toUpperCase()• substring(int beginIndex)

– "unhappy".substring(2) returns "happy" – 0-based index

• substring(int beginIndex, int endIndex)– The substring begins at the specified beginIndex and

extends to the character at index endIndex - 1. Thus the length of the substring is endIndex-beginIndex.

– "hamburger".substring(4, 8) returns "urge" "smiles".substring(1, 5) returns "mile"

• length()• indexOf( char)

Full name format: First Name + Space + Last Name

Change the Full Name to proper format where the first letter of First Name and Last Name changed to uppercase and other letters in

lower case

Example: “david chao” -> “David Chao”

Code Example

public static void main(String[] args) { // TODO code application logic here Scanner sc=new Scanner(System.in); System.out.println("enter full name:"); String FullName=sc.nextLine(); int spaceIndex = FullName.indexOf(" "); String firstName=FullName.substring(0,spaceIndex); String lastName=FullName.substring(spaceIndex+1); String newFullName=proper(firstName) + " " + proper(lastName); System.out.println("Proepr full name:" + newFullName); } public static String proper(String Name){ return Name.substring(0,1).toUpperCase()+ Name.substring(1).toLowerCase(); }

Character class

• isDigit(char)• isLetter(char)

Is a string containing digits only?public static boolean isNumeric(String s){ int i=0; boolean foundLetter=false; for (i=0;i<=s.length()-1;++i){ if (Character.isLetter(s.charAt(i))){ foundLetter=true; break; } } if (foundLetter) return false; else return true; }

Exercise

• Write a isAlpha procedure to determine if a string contains only letters of A-Z.

• Social Security Number format is : ddd-dd-dddd where d is a digit of 0-9. Write a procedure to test if the social security number entered by a user is valid.