Comparator与Comparable的区别
2013-04-17 11:12
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当需要排序的集合或数组不是单纯的数字类型的时候,通常可以使用Comparator或Comparable,以简单的方式实现对象排序或自定义排序。
Comparator和Comparable的区别如下:
Comparable用在对象本身,说明这个对象是可以被比较的,也就是说可以被排序的。(String和Integer之所以可以比较大小,是因为它们都实现了Comparable接口,并实现了compareTo()方法)。
Comparator用在对象外面,相当于定义了一套排序算法来排序。
下面通过具体的例子来理解Comparator和Comparable的区别:
Java代码
package com.tianjf;
import java.util.Arrays;
public class User implements Comparable<Object> {
private String id;
private int age;
public User(String id, int age) {
this.id = id;
this.age = age;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
@Override
public int compareTo(Object o) {
return this.age - ((User) o).getAge();
}
/**
* 测试方法
*/
public static void main(String[] args) {
User[] users = new User[] { new User("a", 30), new User("b", 20) };
Arrays.sort(users);
for (int i = 0; i < users.length; i++) {
User user = users[i];
System.out.println(user.getId() + " " + user.getAge());
}
}
}
Java代码
package com.tianjf;
import java.util.Arrays;
import java.util.Comparator;
public class MyComparator implements Comparator<Object> {
@Override
public int compare(Object o1, Object o2) {
return toInt(o1) - toInt(o2);
}
private int toInt(Object o) {
String str = (String) o;
str = str.replaceAll("一", "1");
str = str.replaceAll("二", "2");
str = str.replaceAll("三", "3");
return Integer.parseInt(str);
}
/**
* 测试方法
*/
public static void main(String[] args) {
String[] array = new String[] { "一", "三", "二" };
Arrays.sort(array, new MyComparator());
for (int i = 0; i < array.length; i++) {
System.out.println(array[i]);
}
}
}
Comparator和Comparable的区别如下:
Comparable用在对象本身,说明这个对象是可以被比较的,也就是说可以被排序的。(String和Integer之所以可以比较大小,是因为它们都实现了Comparable接口,并实现了compareTo()方法)。
Comparator用在对象外面,相当于定义了一套排序算法来排序。
下面通过具体的例子来理解Comparator和Comparable的区别:
Comparable
Java代码package com.tianjf;
import java.util.Arrays;
public class User implements Comparable<Object> {
private String id;
private int age;
public User(String id, int age) {
this.id = id;
this.age = age;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
@Override
public int compareTo(Object o) {
return this.age - ((User) o).getAge();
}
/**
* 测试方法
*/
public static void main(String[] args) {
User[] users = new User[] { new User("a", 30), new User("b", 20) };
Arrays.sort(users);
for (int i = 0; i < users.length; i++) {
User user = users[i];
System.out.println(user.getId() + " " + user.getAge());
}
}
}
Comparator
Java代码package com.tianjf;
import java.util.Arrays;
import java.util.Comparator;
public class MyComparator implements Comparator<Object> {
@Override
public int compare(Object o1, Object o2) {
return toInt(o1) - toInt(o2);
}
private int toInt(Object o) {
String str = (String) o;
str = str.replaceAll("一", "1");
str = str.replaceAll("二", "2");
str = str.replaceAll("三", "3");
return Integer.parseInt(str);
}
/**
* 测试方法
*/
public static void main(String[] args) {
String[] array = new String[] { "一", "三", "二" };
Arrays.sort(array, new MyComparator());
for (int i = 0; i < array.length; i++) {
System.out.println(array[i]);
}
}
}
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