First look at the respective general difference between the two interfaces:
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Comparable is ordering interfaces, commonly used in the natural order; if a class implements the Comparable interface, it means "This class supports sorting."
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Comparator comparator is commonly used in order if necessary to be precisely controlled; if we need to control a plurality of objects of a class of order, can create a "class Comparator" to sort.
Code to look through them to achieve the effect of different
The main code comparable internal comparator
public class Dayimplements Comparable {
private int year;
public Day(int year) {
this.year = year;
}
/**
* @desc 重写compareTo函数。通过year来比较，如果return 的大于0 则当前类排在比较类的后面
* 如果return 的小于0 则当前类排在比较类的前面
*/
public int compareTo(Day otherDay) {
return year - otherDay.year;
}
@Override
public String toString() {
return "year=" +year;
}
public int getYear() {
return year;
}
}
复制代码Outside the main code comparator comparator
public class AscOperation implements Comparator<Day> {
/**
* @desc compare函数。通过year来比较，如果return 的大于0 则前一位排在后一位的后面
* 为升序，如果return 的小于0 则前一位排在后一位的的前面，为降序
*/
public int compare(Day day1, Day day2) {
return day1.getYear() - day2.getYear();
}
}
复制代码The client calling code
public class Main {
public static void main(String[] args){
List days =new ArrayList();
days.add(new Day(2018));
days.add(new Day(2017));
days.add(new Day(2019));
//内部实现排序
Collections.sort(days);
System.out.printf("list:%s\n",days);
//依靠外部方法实现排序
Collections.sort(days,new DescOperation());
System.out.printf("list:%s\n",days);
Collections.sort(days,new AscOperation());
System.out.printf("list:%s\n",days);
}
}
复制代码