java 错误信息：Collections 类型中的 sort(List<T>) 方法不适用于参数 (ArrayList<Date>)
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Error Message: The method sort(List<T>) in the type Collections is not applicable for the arguments (ArrayList<Date>)
提问by JKS7
Keep getting error message, but don't know why. Can't get code to sort the list using Collections.sort()
不断收到错误消息，但不知道为什么。无法获取使用 Collections.sort() 对列表进行排序的代码
Here is what I have. 3 java files.
这是我所拥有的。3个java文件。
The Interface file.
接口文件。
public interface Comparable<T> {
public int compareTo(T other);
}
The Class file.
类文件。
public class Date implements Comparable<Date>{
private int year;
private int month;
private int day;
public Date(int month, int day, int year){
this.month = month;
this.day = day;
this.year = year;
}
public int getYear(){
return this.year;
}
public int getMonth(){
return this.month;
}
public int getDay(){
return this.day;
}
public String toString(){
return month + "/" + day + "/" + year;
}
public int compareTo(Date other){
if (this.year!=other.year){
return this.year-other.year;
} else if (this.month != other.month){
return this.month-other.month;
} else {
return this.day-other.day;
}
}
}
}
The Client class
客户类
import java.util.*;
public class DateTest{
public static void main(String[] args){
ArrayList<Date> dates = new ArrayList<Date>();
dates.add(new Date(4, 13, 1743)); //Jefferson
dates.add(new Date(2, 22, 1732)); //Washington
dates.add(new Date(3, 16, 1751)); //Madison
dates.add(new Date(10, 30, 1735)); //Adams
dates.add(new Date(4, 28, 1758)); //Monroe
System.out.println(dates);
Collections.sort(dates);
System.out.println("birthdays = "+dates);
}
}
The error message I get is "The method sort(List) in the type Collections is not applicable for the arguments (ArrayList)"
我得到的错误消息是“类型集合中的方法 sort(List) 不适用于参数 (ArrayList)”
采纳答案by Sleiman Jneidi
Because Collections.sortexpects java.lang.Comparableand not your Comparable interface, change your Dateclass to implement the java.lang.Comparable.
因为Collections.sortexpectsjava.lang.Comparable而不是您的 Comparable 接口，请更改您的Date类以实现java.lang.Comparable.
public class Date implements java.lang.Comparable<Date>{
..
}
If you still want to define your own Comparable for some reasons and you still want to use Collections.sort then the your Comparablehas to be java.util.Comparable
如果由于某些原因你仍然想定义你自己的 Comparable 并且你仍然想使用 Collections.sort 那么你Comparable必须是java.util.Comparable
interface Comparable<T> extends java.lang.Comparable<T> {
}
回答by Lajos Arpad
Your problem is that with the line of
你的问题是
import java.util.*;
you import java.util.Dateas well. Dateis therefore ambivalent :)
你也导入java.util.Date。Date因此是矛盾的:)
