Introduction to two collection sorting methods in Java
- 2020-04-01 03:30:13
- OfStack
Direct code:
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
/**
*
* <p>
* ClassName CollectionsSort
* </p>
* <p>
* Description This paper mainly introduces two kinds of sorting algorithms of sets <br/>
* The first: java.util.Collections.sort(java.util.List) , requires that the ordered elements be implemented java.lang.Comparable interface <br/>
* The second: java.util.Collections.sort(java.util.List, java.util.Comparator) , this method requires implementation java.util.Comparator interface <br/>
* Third: the following example is used correctly int Type attribute sort, right String Attribute sorting can be done using the following methods <br/>
* public int compareTo(Cat o){return this.getName().compareTo(o.getName(0);}<br/>
* Fourth: compareTo() Description of function <br/>
* if The results of ;<br/>
* <0 a<b ;<br/>=
* ==0 a==b;<br/>
* >=0 a>b;
* </p>
*
* @author wangxu wangx89@126.com
* <p>
* Date 2014-9-16 In the afternoon 04:52:57
* </p>
* @version V1.0
*
*/
public class CollectionsSort {
public static void main(String[] args) {
//Method1 (); Test the first method
method2();//Test the second method
}
public static void method1() {
List<Cat> list = new ArrayList<Cat>();
Cat c = new Cat("a", 10);
list.add(c);
c = new Cat("b", 20);
list.add(c);
c = new Cat("c", 3);
list.add(c);
//Sort the output in ascending order
Collections.sort(list);
System.out.println(list);
//Sort the output in descending order
Collections.sort(list, Collections.reverseOrder());
System.out.println(list);
}
public static void method2() {
List<Cat> list = new ArrayList<Cat>();
Cat c = new Cat("a", 10);
list.add(c);
c = new Cat("b", 20);
list.add(c);
c = new Cat("c", 3);
list.add(c);
Comparator<Cat> catComparator = new Cat();
//Sort the output in ascending order
Collections.sort(list, catComparator);
System.out.println(list);
//Sort the output in descending order
catComparator = Collections.reverseOrder(catComparator);
Collections.sort(list, catComparator);
System.out.println(list);
}
}
class Cat implements Comparable<Cat>, Comparator<Cat> {
private int age;
private String name;
public Cat() {
}
public Cat(String name, int age) {
this.age = age;
this.name = name;
}
public int getAge() {
return this.age;
}
public String getName() {
return this.name;
}
public void setAge(int age) {
this.age = age;
}
public void setName(String name) {
this.name = name;
}
//If the Comparable interface is implemented, do not override the method
@Override
public int compareTo(Cat o) {
// TODO Auto-generated method stub
return this.age - o.age;
}
@Override
public String toString() {
// TODO Auto-generated method stub
return " Name: " + getName() + ", Age: " + getAge();
}
//Implement the Comparator interface and override the method
@Override
public int compare(Cat o1, Cat o2) {
// TODO Auto-generated method stub
return o1.getAge() - o2.getAge();
}
}