算法理论参考：http://www.biaodianfu.com/fackbook-facemash-algorithm.html

实现：

import java.util.List;

public class User {

private String name; //用户名

private double integral; //积分

private double rank; //排名

public User(String name,double integral,int rank){

this.name = name;

this.integral = integral;

this.rank = rank;

}

public User(){

}

/**

* 得到用户积分排名

* @return

*/

public int getUserRanking(){

int result = 0;

return result;

}

public String getName() {

return name;

}

public String getNameString() {

return getName();

}

public Double getIntegral(){

return integral;

}

public double getIntegralString()

{

return getIntegral();

}

public void getNewIntegral(double a){

this.integral = a;

}

public double getRank(){

return rank;

}

public double getRankString()

{

return getRank();

}

public void getNewRank(double a){

this.rank = a;

}

/**

* 得到用户名 积分 排名次

* @return

*/

public String getUserString()

{

return getRankString()+": "+getNameString()+" "+

" "+getIntegralString();

}

/**

* 打印用户信息

* @return

*/

public static String getOutputUser(List User)

{

String result="";

for (int i = 0; i < User.size(); i++)

{

User item=(User)User.get(i);

result+=item.getUserString()+"\r\n";

}

return result;

}

}

import java.util.ArrayList;import java.util.Comparator;

import java.util.List;

import java.util.ArrayList;

import java.util.Collections;

public class UserItem {

public static void main(String[] args)

{

// TODO Auto-generated method stub

test1();

}

public static void test1()

{

User p=new User("WangLei",0.55,1);

User p2=new User("YangJiang",0.54,2);

User p3=new User("XuePeng",0.53,3);

User p4=new User("ZhuKai",0.52,4);

User p5=new User("ZhenShan",0.51,5);

List list=new ArrayList();

list.add(p);

list.add(p2);

list.add(p3);

list.add(p4);

list.add(p5);

System.out.println(User.getOutputUser(list));

match aa = new match();

aa.setUser(p,p2);

aa.setExpect();

aa.setScore();

p.getNewIntegral(aa.setIntegral_a());

p2.getNewIntegral(aa.setIntegral_b());

aa.setUser(p3,p4);

aa.setExpect();

aa.setScore();

p3.getNewIntegral(aa.setIntegral_a());

p4.getNewIntegral(aa.setIntegral_b());

aa.setUser(p3,p5);

aa.setExpect();

aa.setScore();

p3.getNewIntegral(aa.setIntegral_a());

p5.getNewIntegral(aa.setIntegral_b());

aa.setUser(p2,p4);

aa.setExpect();

aa.setScore();

p2.getNewIntegral(aa.setIntegral_a());

p4.getNewIntegral(aa.setIntegral_b());

System.out.println(User.getOutputUser(list));

comparatorUser comparator=new comparatorUser();

Collections.sort(list, comparator);

for (int i=0;i

User user_temp=(User)list.get(i);

user_temp.getNewRank(list.size()-i);

}

System.out.println(User.getOutputUser(list));

}

}

import java.lang.Math;

public class match {

private User user_a;

private User user_b;

private double expect_a = 0;

private double expect_b = 0;

private double score_a = 0;

private double score_b = 0;

private double score = 0;

/**

* 得到比赛结果

* @return

*/

public double getScore()

{

if(score == 0)

{

score = 1;

}

else

{

score = 0;

}

return score;

}

//public static long pow(double x,double y)

/**

* 得到成功期望

* @return

*/

public double getExpect_a()

{

double result = 0;

//1/(1+10^((Ib-Ia)/400))

result = 1/(1 + Math.pow(10, (user_b.getIntegral()-user_a.getIntegral())/400));

return result;

}

public double getExpect_b()

{

double result = 0;

//1/(1+10^((Ia-Ib)/400))

result = 1/(1 + Math.pow(10, (user_a.getIntegral()-user_b.getIntegral())/400));

return result;

}

/**

* 得到比赛后积分

* @return

*/

public double setIntegral_a()

{

//user_a.getIntegral() = user_a.getIntegral() + score_a - expect_a

return user_a.getIntegral() + score_a - expect_a;

}

public double setIntegral_b()

{

return user_b.getIntegral() + score_b - expect_b;

}

public void setUser(User a,User b)

{

this.user_a = a;

this.user_b = b;

}

public void setExpect()

{

this.expect_a = getExpect_a();

this.expect_b = getExpect_b();

}

public void setScore()

{

this.score_a = getScore();

this.score_b = getScore();

}

}

import java.util.Comparator;

import java.util.List;

import java.util.ArrayList;

import java.util.Collections;

public class comparatorUser implements Comparator{

public int compare(Object arg0, Object arg1) {

User user0=(User)arg0;

User user1=(User)arg1;

int flag =0;

flag = user0.getIntegral().compareTo(user1.getIntegral());

return flag;

}

}

学习心得：

1 import java.util.List;

import java.util.ArrayList;

熟悉List与ArrayList类的部分用法，如插入等操作；

扩展：http://blog.sina.com.cn/s/blog_68f262210100mape.html

http://jingyan.baidu.com/article/851fbc37d844553e1f15abe1.html

2 import java.lang.Math;

熟悉Math类下指数运算；

扩展：http://wxb-j2ee.iteye.com/blog/1010258

http://blog.csdn.net/lixiang0522/article/details/7557851

http://www.cnblogs.com/ksuifeng/archive/2010/03/24/1693856.html

3 import java.util.Comparator;

import java.util.Collections;

熟悉Comparator与Collections类，结合ArrayList类，实现数组的排序；

扩展：http://www.blogjava.net/zygcs/archive/2008/01/17/176032.html

http://www.cnblogs.com/fzzl/archive/2010/08/14/1799408.html

http://blog.csdn.net/toweryangtao/article/details/7518325

4 解决问题：

java 提示cannot invoke compareTo(double) on the primitive type double

原因：

错误代码缘由：flag = user0.getIntegral().compareTo(user1.getIntegral());

解决办法： 把对象的getIntegral方法设为Double 而不是double；

public Double getIntegral(){

return integral;

}

5 MyEclipse

http://www.baidu.com/s?wd=myeclipse字体大小设置&tn=11000002_ie_dg