这周总算还是完成任务了hhh
运行代码:
1 package hw2; 2 /* Date.java */ 3 4 import java.io.*; 5 6 public class Date { 7 private int month; 8 private int day; 9 private int year; 10 /** Constructs a date with the given month, day and year. If the date is 11 * not valid, the entire program will halt with an error message. 12 * @param month is a month, numbered in the range 1...12. 13 * @param day is between 1 and the number of days in the given month. 14 * @param year is the year in question, with no digits omitted. 15 */ 16 public Date(int month, int day, int year) { 17 if(isValidDate(month,day,year)){ 18 this.month=month; 19 this.day=day; 20 this.year=year; 21 } 22 else 23 System.exit(0); 24 } 25 /** Constructs a Date object corresponding to the given string. 26 * @param s should be a string of the form "month/day/year" where month must 27 * be one or two digits, day must be one or two digits, and year must be 28 * between 1 and 4 digits. If s does not match these requirements or is not 29 * a valid date, the program halts with an error message. 30 */ 31 public Date(String s) { 32 if(s.matches("\d{1,2}\/\d{1,2}\/\d{1,4}")){ 33 String[]a=s.split("/"); 34 month=Integer.parseInt(a[0]); 35 day=Integer.parseInt(a[1]); 36 year=Integer.parseInt(a[2]); 37 }else 38 System.exit(0); 39 } 40 41 /** Checks whether the given year is a leap year. 42 * @return true if and only if the input year is a leap year. 43 */ 44 public static boolean isLeapYear(int year) { 45 if((year%4==0&&year%100!=0)||(year%400==0)) { 46 return true; } 47 else return false; 48 } 49 50 /** Returns the number of days in a given month. 51 * @param month is a month, numbered in the range 1...12. 52 * @param year is the year in question, with no digits omitted. 53 * @return the number of days in the given month. 54 */ 55 public static int daysInMonth(int month, int year) { 56 switch(month) { 57 case 4:case 6:case 9:case 11: 58 return 30; 59 case 2:if(isLeapYear(year))return 29;else return 28; 60 default: 61 return 31; 62 } 63 } 64 65 /** Checks whether the given date is valid. 66 * @return true if and only if month/day/year constitute a valid date. 67 * 68 * Years prior to A.D. 1 are NOT valid. 69 */ 70 public static boolean isValidDate(int month, int day, int year) { 71 if(year>0&&day<=daysInMonth(month,year)&&month<=12){ 72 return true;} 73 else return false; 74 } 75 76 /** Returns a string representation of this date in the form month/day/year. 77 * The month, day, and year are expressed in full as integers; for example, 78 * 12/7/2006 or 3/21/407. 79 * @return a String representation of this date. 80 */ 81 public String toString() { 82 return(this.month+"/"+this.day+"/"+this.year); 83 } 84 85 /** Determines whether this Date is before the Date d. 86 * @return true if and only if this Date is before d. 87 */ 88 public boolean isBefore(Date d) { 89 if(this.year<d.year)return true; 90 else if(this.year==d.year&&this.month<d.month)return true; 91 else if(this.year==d.year&&this.month==d.month&&this.day<d.day)return true; 92 else return false; 93 } 94 95 /** Determines whether this Date is after the Date d. 96 * @return true if and only if this Date is after d. 97 */ 98 public boolean isAfter(Date d) { 99 if(isBefore(d)||(this.year==d.year&&this.month==d.month&&this.day==d.day)) 100 return false; 101 else return true; 102 103 } 104 105 /** Returns the number of this Date in the year. 106 * @return a number n in the range 1...366, inclusive, such that this Date 107 * is the nth day of its year. (366 is used only for December 31 in a leap 108 * year.) 109 */ 110 public int dayInYear() { 111 int num=0; 112 for(int i=0;i<this.month;i++) 113 num+=daysInMonth(i,this.year); 114 num+=this.day; 115 return num; 116 } 117 118 /** Determines the difference in days between d and this Date. For example, 119 * if this Date is 12/15/2012 and d is 12/14/2012, the difference is 1. 120 * If this Date occurs before d, the result is negative. 121 * @return the difference in days between d and this date. 122 */ 123 public int difference(Date d) { 124 if (isAfter(d)) { 125 int diff=0; 126 for(int i=d.year;i<this.year;i++) { 127 if(isLeapYear(i)) diff+=366; 128 else diff+=365;} 129 int diffday=this.dayInYear()-d.dayInYear(); 130 return diff+diffday; 131 } 132 else if (isBefore(d)) { // replace this line with your solution 133 return -d.difference(this); 134 } 135 else return 0; 136 } 137 138 public static void main(String[] argv) { 139 System.out.println(" Testing constructors."); 140 Date d1 = new Date(1, 1, 1); 141 System.out.println("Date should be 1/1/1: " + d1); 142 d1 = new Date("2/4/2"); 143 System.out.println("Date should be 2/4/2: " + d1); 144 d1 = new Date("2/29/2000"); 145 System.out.println("Date should be 2/29/2000: " + d1); 146 d1 = new Date("2/29/1904"); 147 System.out.println("Date should be 2/29/1904: " + d1); 148 149 d1 = new Date(12, 31, 1975); 150 System.out.println("Date should be 12/31/1975: " + d1); 151 Date d2 = new Date("1/1/1976"); 152 System.out.println("Date should be 1/1/1976: " + d2); 153 Date d3 = new Date("1/2/1976"); 154 System.out.println("Date should be 1/2/1976: " + d3); 155 156 Date d4 = new Date("2/27/1977"); 157 Date d5 = new Date("8/31/2110"); 158 159 /* I recommend you write code to test the isLeapYear function! */ 160 161 System.out.println(" Testing before and after."); 162 System.out.println(d2 + " after " + d1 + " should be true: " + 163 d2.isAfter(d1)); 164 System.out.println(d3 + " after " + d2 + " should be true: " + 165 d3.isAfter(d2)); 166 System.out.println(d1 + " after " + d1 + " should be false: " + 167 d1.isAfter(d1)); 168 System.out.println(d1 + " after " + d2 + " should be false: " + 169 d1.isAfter(d2)); 170 System.out.println(d2 + " after " + d3 + " should be false: " + 171 d2.isAfter(d3)); 172 173 System.out.println(d1 + " before " + d2 + " should be true: " + 174 d1.isBefore(d2)); 175 System.out.println(d2 + " before " + d3 + " should be true: " + 176 d2.isBefore(d3)); 177 System.out.println(d1 + " before " + d1 + " should be false: " + 178 d1.isBefore(d1)); 179 System.out.println(d2 + " before " + d1 + " should be false: " + 180 d2.isBefore(d1)); 181 System.out.println(d3 + " before " + d2 + " should be false: " + 182 d3.isBefore(d2)); 183 184 System.out.println(" Testing difference."); 185 System.out.println(d1 + " - " + d1 + " should be 0: " + 186 d1.difference(d1)); 187 System.out.println(d2 + " - " + d1 + " should be 1: " + 188 d2.difference(d1)); 189 System.out.println(d3 + " - " + d1 + " should be 2: " + 190 d3.difference(d1)); 191 System.out.println(d3 + " - " + d4 + " should be -422: " + 192 d3.difference(d4)); 193 System.out.println(d5 + " - " + d4 + " should be 48762: " + 194 d5.difference(d4)); 195 } 196 }
运行结果：
程序运行成功之前曾经在一个地方卡了大半天。。。就是在public Date(int month, int day, int year）这个地方，
我之前写的代码
1 public Date(int month, int day, int year) { 2 if(isValidDate(month,day,year)){ 3 this.month=month; 4 this.day=day; 5 this.year=year; 6 } 7 else 8 System.out.println("Input Error!"); 9 System.exit(0); 10 }
也就是在 System.exit(0); 之前加了一行System.out.println("Input error!");想让它显示个错误
结果是这样的，也不会报错，正常运行，但是后面什么都不输出
百思不得其解。。。看到的大神求解答一波~~？