终于完成了hw2，打卡打卡，想说的都在备注里了，今天太晚了，哪天再过来更，需要总结一下编程思路什么的。这次作业学到了很多啊，强装围笑鼓个掌吧。
/* Date.java */ import java.io.*; class Date { private String Year; private String Month; private String Day; private int Y; private int M; private int D; private int n; private int firstSlash; private int secondSlash; /* 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)){ M=month; D=day;//只有在date有效前提下赋值，赋值语句要在if语句里 Y=year; } else{System.out.println("inValidDate"); System.exit(0); } } /** 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) { StringBuilder z=new StringBuilder(s);//通过把类型转换为StringBuilder firstSlash=z.indexOf("/"); secondSlash=z.indexOf("/",firstSlash+1);//识别两个“／”的index Year=z.substring(secondSlash+1, s.length());//将String转化为年月日三部分 Month=z.substring(0, firstSlash); Day=z.substring(firstSlash+1, secondSlash); int m=Integer.parseInt(Month); int d=Integer.parseInt(Day); int y=Integer.parseInt(Year); //尝试用this.(m.d.y) 失败了，要求constructor必须在第一行，so有没有更好的方法?? if(Year.length()>4||Year.length()==0||Month.length()>2||Month.length()==0 ||Day.length()>2||Day.length()==0||!isValidDate(m, d, y)){ /*判断年月日字符数是否符合要求,引用isValidDate()，但不能只用这个盘踞， * 保证在002这种月份出现的情况下仍能正确判断 */ System.out.println("Error-invalidInputString"); System.exit(0); } else { M=m; D=d; Y=y; //同第一个constructor，在符合要求之后才进行赋值 } } /** 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%4!=0||(year%4==0&&year%100==0&&year%400!=0)){ return false; } return true; } // 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) { if(month==1||month==3||month==5||month==7||month==8||month==10||month==12){ return 31; } else if(month==4||month==6||month==9||month==11){ return 30;}else if(month==2){ if(Date.isLeapYear(year)){ return 29; } } return 28;//返回值语句至少有一句必须在if braces外面 } /** 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) { if(year>=0&&year<=9999&&month>0&&month<13&&day<=daysInMonth(month, year)&&day>0){ return true;} 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 (M+"/"+D+"/"+Y); // 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(Y<d.Y||(Y==d.Y&&M<d.M)||(Y==d.Y&&M==d.M&&D<d.D)){ return true; } 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(Y==d.Y&&D==d.D&&M==d.M){ return false; // 不能直接用isBefore()的非，需要增加日期相同的情况 } return !isBefore(d); } // 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() { n=0; for(int i=1;i<M;i++){ n=daysInMonth(i, Y)+n;// 求本月之前月份天数总和 } n=n+D; //加上本月的日期 return n; // 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 numberOfDaysInYear(){ int k1=0; for(int i=0;i<Y;i++){ if(isLeapYear(i)){ k1=366+k1; }else{ k1=365+k1; } } k1=k1+dayInYear(); return k1; } //以上为新建method 为了方便下面的difference（）做减法，避免重复代码 public int difference(Date d) { return numberOfDaysInYear()-d.numberOfDaysInYear(); // 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"); /* 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)); } }
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