| ITEC 120 |
| 2008spring |
| ibarland, jdymacek |
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home—info—exams—lectures—labs—hws
Recipe—Laws—lies—syntax—java.lang docs—java.util docs
/** Is this Date valid?
* @return true iff the year,month,day correspond to an actual Julian Date.
*/
boolean isValid() {
// Remember the month & day in a variable w/ a short name, for future use:
int m = this.getMonth();
int d = this.getDay();
if ((this.getYear() == 0) || (d <= 0) || (m <= 0) || (m > 12)) {
return false;
}
// year and m are valid; check d not too large:
else if (m == 2) {
if (this.isLeapYear(this.getYear())) {
return (d <= 29);
}
else {
return (d <= 28);
}
}
else if ((m==4) || (m==6) || (m==9) || (m==11)) {
return (d <= 30);
}
else {
return (d <= 31);
}
/* The version above checks for Feb, then Apr,Jun,Sep,Nov,
* without mentioning the other seven months explicitly.
* While doing so would certainly be reasonable, our version actually
* reflects the old1 mnemonic:
*
* Thirty days hath November,
* April, June, and September;
* All the rest have thirty-one,
* Except for February alone,
* Which hath twenty-eight days clear,
* And twenty-nine in each leap year,
*
* Our code hews surprisingly close to this mnemonic -- having code
* which corresponds to how we think about the problem in real life
* is the 0'th of The Laws of Programming!
*/
}
/** Is a given year a leap-year?
* @param y The year to inquire about (e.g. 2008).
* @return whether yr is a leap-year.
*/
boolean isLeapYear(int y) {
return ((y%4) == 0) && ( ((y%100) != 0) || ((y%400)==0) );
}
/** Is this Date the same as another? (Same year, month, and day?)
* @param other The Date to compare this Date to.
* @return whether this Date represents the same day as `other`.
* The result is only guaranteed when ((this.isValid()) && (other.isValid())).
*/
boolean sameDayAs( Date other ) {
// REPLACE THE STUB WITH YOUR ACTUAL CODE
}
/** Does this date come before another?
* @param other The Date to compare this Date to.
* @return whether this Date comes before `other`.
* The result is only guaranteed when ((this.isValid()) && (other.isValid())).
*/
boolean comesBefore( Date other ) {
return false; // REPLACE THE STUB WITH YOUR ACTUAL CODE
}
/** Return the day after this one.
* @return a Date object corresponding to the day after this Date.
* `this` must be valid. The return date will be valid.
*/
Date nextDay() {
Date dayPlus = new Date( this.getYear(), this.getMonth(), this.getDay()+1 );
return dayPlus;
// REPLACE THE STUB WITH YOUR ACTUAL CODE
// We must check whether dayPlus is a valid day, and if not,
// make a *different* new Date ...
}
/** Return a Date representing the current date (in real time).
* @return a Date representing the current date (in real time).
*/
Date today() {
java.util.Calendar c = java.util.Calendar.getInstance();
return new Date( c.get(java.util.Calendar.YEAR),
c.get(java.util.Calendar.MONTH)+1, // Calendar starts w/ month 0.
c.get(java.util.Calendar.DAY_OF_MONTH) );
}
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Look at the new source you pasted in. Note that some methods have been written for you (isValid, isLeapYear).
However, some methods are left for you to write: sameDayAs, comesBefore, nextDay.
1Versions are documented back to the 1400s! (source: Wikipedia) ↩
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| ©2008, Ian Barland, Radford University Last modified 2008.Feb.27 (Wed) |
Please mail any suggestions (incl. typos, broken links) to iba�rland  rad�ford.edu |
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