代码如下：
1）Date(String s)那块我注释出来的那一块，把for语句里改成j<s.length()也可以运行出来。
2）想问一下大家是怎么想到用match和split的方法的？
3）difference那块可以用下面两句改写，很巧妙。
else if (isBefore(d)) 133 return -d.difference(this);
4）作业做了很久，但真的有对之前lecture没懂的地方有了更多的认识
package homework2;
/* Date.java */
import java.io.*;
class Date {
private int month;
private int day;
private int year;
/* Put your private data fields here. */
/** Constructs a date with the given month, day and year. If the date is
* not valid, the entire program will halt with an error message.
* @param month is a month, numbered in the range 1...12.
* @param day is between 1 and the number of days in the given month.
* @param year is the year in question, with no digits omitted.
*/
public Date(int month, int day, int year) {
if(isValidDate(month,day,year)!=true) {
System.out.println("The date is not valid");
}else {
this.day=day;
this.month=month;
this.year=year;
}
}
/** Constructs a Date object corresponding to the given string.
* @param s should be a string of the form "month/day/year" where month must
* be one or two digits, day must be one or two digits, and year must be
* between 1 and 4 digits. If s does not match these requirements or is not
* a valid date, the program halts with an error message.
*/
public Date(String s) {
if(s.matches("\d{1,2}\/\d{1,2}\/\d{1,4}")){
String[] d=s.split("/");
month=Integer.parseInt(d[0]);
day=Integer.parseInt(d[1]);
year=Integer.parseInt(d[2]);
}else System.out.println("error Date(String s)");
}
/* int[] line=new int[2];
int i=0;
for(int j=0;j<=s.length();j++) {
char result=s.charAt(j);
if(result=='/') {
line[i]=j;
i++;
}
}
int stringmonth= Integer.parseInt(s.substring(0,line[0]));
int stringday= Integer.parseInt(s.substring(line[0]+1,line[1]));
int stringyear= Integer.parseInt(s.substring(line[1]+1,s.length()));
if(stringmonth>=1&&stringmonth<=12) {
if(stringday>=1&&stringday<=31) {
if(stringyear>=1&&stringyear<=9999) {
month=stringmonth;
day=stringday;
year=stringyear;
}else {
System.out.println("error");
}
}
}
}*/
/** Checks whether the given year is a leap year.
* @return true if and only if the input year is a leap year.
*/
public static boolean isLeapYear(int year) {
if((year%400==0)||((year%400!=0)&&(year%100!=0)&&(year%4==0))) {
return true;
}else {
return false;
}
// replace this line with your solution
}
/** Returns the number of days in a given month.
* @param month is a month, numbered in the range 1...12.
* @param year is the year in question, with no digits omitted.
* @return the number of days in the given month.
*/
public static int daysInMonth(int month, int year) {
/*System.out.print("days in month "+month+" is:");*/
if(month==2) {
if(isLeapYear(year)) {
return 29;
}else return 28;
}else
switch(month) {
case 4:
case 6:
case 9:
case 11:
return 30;
default:
return 31;
}
}
// replace this line with your solution
/** Checks whether the given date is valid.
* @return true if and only if month/day/year constitute a valid date.
*
* Years prior to A.D. 1 are NOT valid.
*/
public static boolean isValidDate(int month, int day, int year) {
/*System.out.print("The given date "+month+"/"+day+"/"+year+" is:");*/
if(month>=1&&month<=12&&day>=1&&day<=daysInMonth(month,year)&&year>=1) {
return true;
}else {
return false;
}
}
// replace this line with your solution
/** Returns a string representation of this date in the form month/day/year.
* The month, day, and year are expressed in full as integers; for example,
* 12/7/2006 or 3/21/407.
* @return a String representation of this date.
*/
public String toString() {
return month+"/"+day+"/"+year; // replace this line with your solution
}
/** Determines whether this Date is before the Date d.
* @return true if and only if this Date is before d.
*/
public boolean isBefore(Date d) {
if (this.year<d.year) {
return true;
}else if(this.year==d.year) {
if(this.month<d.month) {
return true;
}else if(this.month==d.month) {
if(this.day<d.day) {
return true;
}else return false;
}else return false;
} else return false;
// replace this line with your solution
}
/** Determines whether this Date is after the Date d.
* @return true if and only if this Date is after d.
*/
public boolean isAfter(Date d) {
if(!isBefore(d)&&d!=this) {
return true;
}else return false;
// replace this line with your solution
}
/** Returns the number of this Date in the year.
* @return a number n in the range 1...366, inclusive, such that this Date
* is the nth day of its year. (366 is used only for December 31 in a leap
* year.)
*/
public int dayInYear() {
int count=0;
for(int j=this.month-1;j>0;j--) {
count+=daysInMonth(j,this.year);
}
count+=this.day;
return count; // replace this line with your solution
}
/** Determines the difference in days between d and this Date. For example,
* if this Date is 12/15/2012 and d is 12/14/2012, the difference is 1.
* If this Date occurs before d, the result is negative.
* @return the difference in days between d and this date.
*/
public int difference(Date d) {
int total=0;
if(isAfter(d)) {
for(int j=d.year;j<this.year;j++) {
if(isLeapYear(j)) {
total+=366;
}else {
total+=365;
}
}
return (total+this.dayInYear()-d.dayInYear());
}else
if(isBefore(d)) {
for(int j=this.year;j<d.year;j++) {
if(isLeapYear(j)) {
total+=366;
}else {
total+=365;
}
}
return -(total+d.dayInYear()-this.dayInYear());
}
else return 0;
}
//replace this line with your solution
public static void main(String[] argv) {
System.out.println("
Testing constructors.");
Date d1 = new Date(1, 1, 1);
System.out.println("Date should be 1/1/1: " + d1);
d1 = new Date("2/4/2");
System.out.println("Date should be 2/4/2: " + d1);
d1 = new Date("2/29/2000");
System.out.println("Date should be 2/29/2000: " + d1);
d1 = new Date("2/29/1904");
System.out.println("Date should be 2/29/1904: " + d1);
d1 = new Date(12, 31, 1975);
System.out.println("Date should be 12/31/1975: " + d1);
Date d2 = new Date("1/1/1976");
System.out.println("Date should be 1/1/1976: " + d2);
Date d3 = new Date("1/2/1976");
System.out.println("Date should be 1/2/1976: " + d3);
Date d4 = new Date("2/27/1977");
Date d5 = new Date("8/31/2110");
System.out.println("
Testing the isLeapYear function!");
int y1=2014;
System.out.println("That "+y1+" is leap year should be:"+isLeapYear(y1));
int y2=1900;
System.out.println("That "+y2+" is leap year should be:"+isLeapYear(y2));
int y3=1600;
System.out.println("That "+y3+" is leap year should be:"+isLeapYear(y3));
int y4=2012;
System.out.println("That "+y4+" is leap year should be:"+isLeapYear(y4));
/* I recommend you write code to test the isLeapYear function! */
System.out.println("
Testing before and after.");
System.out.println(d2 + " after " + d1 + " should be true: " +
d2.isAfter(d1));
System.out.println(d3 + " after " + d2 + " should be true: " +
d3.isAfter(d2));
System.out.println(d1 + " after " + d1 + " should be false: " +
d1.isAfter(d1));
System.out.println(d1 + " after " + d2 + " should be false: " +
d1.isAfter(d2));
System.out.println(d2 + " after " + d3 + " should be false: " +
d2.isAfter(d3));
System.out.println(d1 + " before " + d2 + " should be true: " +
d1.isBefore(d2));
System.out.println(d2 + " before " + d3 + " should be true: " +
d2.isBefore(d3));
System.out.println(d1 + " before " + d1 + " should be false: " +
d1.isBefore(d1));
System.out.println(d2 + " before " + d1 + " should be false: " +
d2.isBefore(d1));
System.out.println(d3 + " before " + d2 + " should be false: " +
d3.isBefore(d2));
System.out.println("
Testing difference.");
System.out.println(d1 + " - " + d1 + " should be 0: " +
d1.difference(d1));
System.out.println(d2 + " - " + d1 + " should be 1: " +
d2.difference(d1));
System.out.println(d3 + " - " + d1 + " should be 2: " +
d3.difference(d1));
System.out.println(d3 + " - " + d4 + " should be -422: " +
d3.difference(d4));
System.out.println(d5 + " - " + d4 + " should be 48762: " +
d5.difference(d4));
}
}
运行结果：
