1.ComParable接口
Comparable接口的定义如下：
public interface Comparable
{
public int compareTo(T o);
}
此方法返回一个int类型的数据，但是此int的值只能是一下三种：
1：表示大于
-1：表示小于
0：表示相等
实例：
package zy.java.lang;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
public class ComparableTest implements Comparable
{
private String id;
private int age;
public ComparableTest(String id,int age)
{
this.id = id;
this.age = age;
}
public String getId()
{
return id;
}
public void setId(String id)
{
this.id = id;
}
public int getAge()
{
return age;
}
public void setAge(int age)
{
this.age = age;
}
@Override
public int compareTo(ComparableTest c)
{
return this.age - c.getAge();
}
public static void main(String[] args)
{
//Collection
ComparableTest ct1 = new ComparableTest("a",39);
ComparableTest ct2 = new ComparableTest("b",31);
ComparableTest ct3 = new ComparableTest("c",38);
List list = new ArrayList();
list.add(ct1);
list.add(ct2);
list.add(ct3);
Collections.sort(list);
for(int i=0;i
{
System.out.println(list.get(i).getId());
}
System.out.println("-------------------------------------------");
//Array
ComparableTest[] ct = new ComparableTest[]{
new ComparableTest("a",39),
new ComparableTest("b",31),
new ComparableTest("c",38)
};
Arrays.sort(ct);
for(int i=0;i
{
System.out.println(ct[i].getId());
}
}
}
2.Comparator接口
如果一个类已经开放完成，但是在此类建立的初期并没有实现Comparable接口，此时肯定是无法进行对象排序操作的，所以为了解决这一的问题，java又定义了另一个比较器的操作接口 Comparator 此接口定义在java.util包中，接口定义如下：
public interface Comparator
{
public int compare(T o1，T o2);
}
实例：
package zy.java.lang;
public class Users
{
private String id;
private int age;
public Users(String id, int age) {
this.id = id;
this.age = age;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
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package zy.java.lang;
import java.util.*;
public class ComparatorTest implements Comparator
{
@Override
public int compare(Users o1, Users o2)
{
return o1.getAge() - o2.getAge();
}
public static void main(String[] agrs)
{
//Collection
Users u1 = new Users("a",33);
Users u2 = new Users("b",31);
Users u3 = new Users("c",38)