Java：构造函数和传递变量出错答案

【问题标题】：Java: Error with constructors and passing variablesJava：构造函数和传递变量出错
【发布时间】：2015-09-30 10:42:29
【问题描述】：

我正在尝试以 dd mm yyyy 格式输入日期，并且必须以 e 格式返回。 G。 Tuesday, 29th September。我是 Java 新手，不确定我的日、月、年类的值是否被返回到主类。 Date date1 = new Date(day1, month1, year1) 有一个错误，说它未定义并使其成为构造函数。如果我将其设为构造函数并运行程序，我会得到类似lab2.Day@659e0bfd 的值。不知道从这里去哪里。

package lab2;

public class Calendar {

//assume all months have 30 days and that 1 January is a Monday;

public static void main(String[] args) { // e.g. input: 29 09 2015

    int in1 = Integer.parseInt(args[0]);
    int in2 = Integer.parseInt(args[1]);
    int in3 = Integer.parseInt(args[2]);

    Day day1 = new Day(in1, in2); // string
    Month month1 = new Month(in2); // string
    Year year1 = new Year(in3); // integer


     Date date1 = new Date(day1, month1, year1); //

    date1.printName(); // e.g. "The date is Tuesday, 29th of September, 2015

}
}

package lab2;

public class Day {
private int day;
private int month;
private int code;
private String name; //e.g. Tuesday 

public Day(int dy, int mth ){
    day = dy;
    month = mth;
    code = ((day*month) % 7);


    // Assigning the day variable number to text //
    switch (code) {
    case 0: name = "Monday";
            break;
    case 1: name = "Tuesday";
            break;
    case 2: name = "Wednesday";
            break;
    case 3: name = "Thursday";
            break;
    case 4: name = "Friday";
            break;
    case 5: name = "Saturday";
            break;
    case 6: name = "Sunday";
            break;
    default: System.out.println("Incorrect Day Entered");}

    }

}

package lab2;

public class Month {

private int month1;
private String monthName;




public Month(int temp1){
    month1=temp1;


switch (month1) {
case 1: monthName = "January";
        break;
case 2: monthName = "February";
        break;
case 3: monthName = "March";
        break;
case 4: monthName = "April";
        break;
case 5: monthName = "May";
        break;
case 6: monthName = "June";
        break;
case 7: monthName = "July";
        break;
case 8: monthName = "August";
        break;
case 9: monthName = "September";
        break;
case 10: monthName = "October";
        break;
case 11: monthName = "November";
        break;
case 12: monthName = "December";
        break;
default: System.out.println("Incorrect Month Error");}


}

}

package lab2;

public class Year {

private int yearNumber;

public Year(int temp2)
{
    yearNumber=temp2;


}
}

package lab2;

public class Date {

private String day;
private String month;
private int year;



 public Date(String temp1, String temp2, int temp3){
    day = temp1;
    month = temp2;
    year = temp3; 
    }



public void printName() {
    System.out.println("The date is " +day+ ", " +month+ ", " +year);
}

}

【问题讨论】：

我投票结束这个问题，因为这个问题属于CodeReview StackExchange。

标签： java date variables constructor

【解决方案1】：

“日期 date1 = new Date(day1, month1, year1)”有错误说它是未定义的并使其成为构造函数。

因为在Date 类中没有像Date(Day d, Month m, Year y) 这样的参数化构造函数。它有构造函数Date(String temp1, String temp2, int temp3)。所以参数类型不同。

代替

Date date1 = new Date(day1, month1, year1);

使用

Date date1 = new Date(day1.name, month1.monthName, year1.yearNumber);

【讨论】：

【解决方案2】：

“日期 date1 = new Date(day1, month1, year1)" 说它是未定义的并使其成为构造函数。如果我使它是一个构造函数并运行程序我得到的值就像 “lab2.Day@659e0bfd”。不知道从这里去哪里。

你得到 lab2.Day@659e0bfd 因为你还没有实现 toString() 方法。在 Day、Month 和 Year 类中实现 toString() 方法，您将获得所需的结果。检查下面的代码 -

 public class Day {
    private int day;
    private int month;
    private int code;
    private String name; //e.g. Tuesday 

    public Day(int dy, int mth ){
        day = dy;
        month = mth;
        code = ((day*month) % 7);


        // Assigning the day variable number to text //
        switch (code) {
        case 0: name = "Monday";
                break;
        case 1: name = "Tuesday";
                break;
        case 2: name = "Wednesday";
                break;
        case 3: name = "Thursday";
                break;
        case 4: name = "Friday";
                break;
        case 5: name = "Saturday";
                break;
        case 6: name = "Sunday";
                break;
        default: System.out.println("Incorrect Day Entered");}

        }
        @Override
        public String toString() {
            return name;
        }

    }

类似的，你可以把 toString() 方法放在 Month 类中

public class Month {

private int month1;
private String monthName;




public Month(int temp1){
    month1=temp1;


switch (month1) {
case 1: monthName = "January";
        break;
case 2: monthName = "February";
        break;
case 3: monthName = "March";
        break;
case 4: monthName = "April";
        break;
case 5: monthName = "May";
        break;
case 6: monthName = "June";
        break;
case 7: monthName = "July";
        break;
case 8: monthName = "August";
        break;
case 9: monthName = "September";
        break;
case 10: monthName = "October";
        break;
case 11: monthName = "November";
        break;
case 12: monthName = "December";
        break;
default: System.out.println("Incorrect Month Error");

        @Override
        public String toString() {
            return monthName;
        }

}

你的年级 -

public class Year {

private int yearNumber;

public Year(int temp2)
{
    yearNumber=temp2;


}

        @Override
        public String toString() {
            return yearNumber;
        }
}

【讨论】：