Code

/*
The result I get is a little different, but I think my code works. 
The println displays:
Wed Nov 05 00:00:00 GMT 2008

Milliseconds since 1/1/1970 = 
1225843200000
*/

int monthInt = 0;
String S = "    <pubDate>Wed, 05 Nov 2008 21:33:50 +0000</pubDate>";
String T = S.trim();
int pref1 = T.indexOf(' '); 
int pref2 = T.indexOf(' ', (pref1+4));
int pref3 = T.indexOf(' ', (pref1+2));
String D = T.substring(pref1+1, pref1+3);
int dayInt = Integer.parseInt(D);
String Y = T.substring(pref2+1, pref2+5);
int yearInt = Integer.parseInt(Y);
String M = T.substring(pref3+1, pref3+4);

String monthNames[] = 
{ "Jan","Feb","Mar","Apr",
  "May","Jun","Jul","Aug",
  "Sep","Oct","Nov","Dec"};
  
for (int i = 0; i < monthNames.length; i++){
 if (M.equals(monthNames[i])){
  monthInt = i;
 } 
}

GregorianCalendar greg = new GregorianCalendar(yearInt, monthInt, dayInt);
Date someDate = greg.getTime();
long millisecondsSince1970 = someDate.getTime();
println(someDate);
println("Milliseconds since 1/1/1970 = " + millisecondsSince1970);

0702 - String method refresher: Scraping and parsing dates

Statement:This five-part assignment is a collection of simple exercises to make sure that you understand (and have used) some of the many String methods that are available to you. In the next assignment (0703), you will use the results of this assignment to produce a display of Twitter posts over time, using data scraped from my (or someone else's) Twitter RSS feed. It goes without saying that you will need to refer to the Java String reference for this assignment.

For this assignment: suppose you have encountered a String S formatted as follows. (This String is from my Twitter RSS feed.) 

String S = "    <pubDate>Wed, 05 Nov 2008 21:33:50 +0000</pubDate>";
  • Note that there are some blank spaces at the beginning of the line. Apply the String.trim() method to String S, to create a new String T in which you have removed the whitespace from the end(s) of the provided line of text.


  • Using the String.substring() method, extract (from the String T) into a new String D the two characters indicating the day-number. Then use the following code to convert this String into an actual integer: 
    int dayInt = Integer.parseInt(D);
  • Then do the same thing for the four-digit year number. Extract its characters into a string Y, and convert this String into an integer, yearInt.
  • Using the String.substring() method again, extract from T into a new String M the three characters which indicate the month. Now Suppose the following arrays have been declared: 
    String monthNames[] = 
{ "Jan","Feb","Mar","Apr",
  "May","Jun","Jul","Aug",
  "Sep","Oct","Nov","Dec"};
    Using a for{} loop, check the month String M to see if it is the same as any of the Strings in the monthNames[] array. If it is, report an integer monthInt, which is the index of the identical String in the monthNames array. IMPORTANT NOTE: In order to make the String comparison test, the == operator will not work; you must use the String.equals() method instead!


  • You should now have three integers that represent components of the date scraped from String S: yearInt, monthInt, and dayInt.
    Below is some code which will convert these integers into a single number, which represents (for this date) the number of milliseconds since 1970. This code uses the GregorianCalendar object and the Date object, both of which are built into Java. (You can get Java documentation about these objects from the links). 
    GregorianCalendar greg = new GregorianCalendar(yearInt, monthInt, dayInt);
Date someDate = greg.getTime();
long millisecondsSince1970 = someDate.getTime();
println(someDate);
println("Milliseconds since 1/1/1970 = " + millisecondsSince1970);
    To confirm that your previous code works correctly, check that the last two println() commands produce the following results: 
    Wed Nov 05 00:00:00 EST 2008
Milliseconds since 1/1/1970 = 1225861200000


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