Comparable接口与Comparator接口主要区别及实例

Comparable接口与Comparator接口主要区别:

1、前者（强烈推荐）是强行对是实现它的每个类的对象进行整体排序，此类被称为该类的自然排序，类的compareTo方法被称为它的自然比较方法，实现此接口的对象列表和（数组）可以通过Collections.sort()或者Arrays.sort()进行自动排序。

2、Comparator位于包java.util下，而Comparable位于包java.lang下，Comparable接口将比较代码嵌入自身类中，而后者在一个独立的类中实现比较。 如果类的设计师没有考虑到Compare的问题而没有实现Comparable接口，可以通过  Comparator来实现比较算法进行排序，并且为了使用不同的排序标准做准备，比如：升序、降序。

3、实现方法int compareTo(T o) 比较对象之间的关系，< >=分别返回负数，正数，零。

4、强烈推荐(x.compareTo(y)==0)==(x.equals(y))这种做法，但不是严格要求这么做。

 

实例：

Comparable接口

 

Person.java

packagecom.comparable.test;

importjava.util.Random;

public class Person implements Comparable<Person> {

         private Randomr = new Random();

         private Stringusername;

         private int age;

         private int id= r.nextInt(100);

         publicString getUsername() {

                  returnusername;

         }

         public void setUsername(String username) {

                  this.username = username;

         }

         public int getAge() {

                  returnage;

         }

         public void setAge(int age) {

                  this.age = age;

         }

         public int getId() {

                  returnid;

         }

         public void setId(int id) {

                  this.id = id;

         }

         public String toString() {

                  return"Person [username=" + username + ",age=" + age

                                   + ", id=" + id + "]";

         }

         public Person(String username,int age) {

                  super();

                  this.username = username;

                  this.age = age;

 

         }

         //override compareTo method

         public int compareTo(Person o) {

                  if(this.id>o.id){

                          return 1;

                  }elseif(this.id==o.id){

                          return 0;

                  }else{

                          return -1;

                  }

/*              if(this.age>o.getAge()){

                          return 1;

                  }elseif(this.age==o.getAge()){

                          return 0;

                  }else{

                          return -1;

                  }*/

         }

}

 

Comparator接口

ComparableTest.java

packagecom.comparable.test;

importjava.util.Arrays;

public class ComparableTest{

         public static void main(String[] args) {

                  Person[] persons =new Person[3];

                  persons[0] =newPerson("zhangsan",10);

                  persons[1]= newPerson("lisi",21);

                  persons[2] = newPerson("wangwu",22);

                  Arrays.sort(persons);

                  for(Person p:persons){

                          System.out.println("-----------------");

                          System.out.print(p.toString());

                          System.out.println("-----------------");

                  }

         }

}

 

ComparatorTest.java

packagecom.comparator.test;

import java.util.ArrayList;

importjava.util.Comparator;

import java.util.List;

importjava.util.Set;

importjava.util.TreeSet;

 

importcom.comparable.test.Person;

 

public class ComparatorTest implements Comparator<Person> {

         public static void main(String[] args) {

                  ComparatorTest comparator = new ComparatorTest();

                  Set<Person> ps = new TreeSet<Person>(comparator);

                  ps.add(new Person("zhangsan",21));

                  ps.add(new Person("jack",19));

                  ps.add(new Person("sun",20));

                  for(Person p:ps){

                          System.out.println("-----------------");

                          System.out.print(p.toString());

                          System.out.println("-----------------");

                  }

         }

         public int compare(Person o1, Person o2) {

                  if(o1.getAge()>o2.getAge()){

                          return 1;

                  }elseif(o1.getAge()==o2.getAge()){

                          return 0;

                  }else{

                          return -1;

                  }

         }

}