Guava使用

Guava中针对集合的 filter和过滤功能

package com.kaishengit;

import com.google.common.base.Function;
import com.google.common.base.Predicate;
import com.google.common.collect.Collections2;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Sets;
import com.kaishengit.entity.User;

import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Set;

public class Test {

    public static void main(String[] args) {

        /*User user = new User();
        user.setId(100);
        user.setFirstName("Jack");

        User user2 = new User();
        user2.setId(101);
        user2.setFirstName("Rose");

        User user3 = new User();
        user3.setId(103);
        user3.setFirstName("Rose2");

        List<User> userList = Lists.newArrayList(user,user2,user3);

        List<User> subList = Lists.newArrayList(Collections2.filter(userList, new Predicate<User>() {
            @Override
            public boolean apply(User user) {
                return user.getFirstName().startsWith("Ro");
            }
        }));

        Set<String> set = Sets.newHashSet();
        Map<String,Object> map = Maps.newHashMap();*/


        /*List<String> nameList = Lists.newArrayList(Collections2.transform(userList, new Function<User, String>() {
            @Override
            public String apply(User f) {
                return f.getFirstName();
            }
        }));*/

       /* List<String> nameList = Lists.newArrayList();

        for(User u : userList) {
            nameList.add(u.getFirstName());
        }*/


        //List<String> list = Lists.newArrayList("A1","A2");

        /*List<String> list = Lists.newArrayList();
        list.add("A1");
        list.add("A2");*/
    }
}

2017-9-26 9-10-29.png guava使用.png guava过滤.png
clipboard.png

缓存 测试

package com.kaishengit.service;

import com.kaishengit.entity.User;
import org.junit.Test;

import static org.junit.Assert.*;

public class UserServiceWithGuavaTest {

    private UserService userService = new UserService();

    @Test
    public void findById() throws Exception {
        User user = userService.findById(7);
        user = userService.findById(7);

        System.out.println(user);
    }

}

配置

package com.kaishengit.service;

import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.kaishengit.dao.UserDao;
import com.kaishengit.entity.User;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;

public class UserServiceWithGuava {

    private UserDao userDao = new UserDao();

    private static Cache<String,User> cache = CacheBuilder.newBuilder()
            .maximumSize(100)//f放一百个数据
            .expireAfterAccess(10,TimeUnit.MINUTES)//天数
            .build();

    public User findById(Integer id) {
        User user = null;
        try {
            user = cache.get("user:" + id, new Callable<User>() {
                @Override
                public User call() {
                    return userDao.findById(id);
                }
            });
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
        return user;
    }



    /*private static LoadingCache<String,User> cache = CacheBuilder
            .newBuilder()
            .maximumSize(100)
            .expireAfterAccess(50, TimeUnit.SECONDS)
            .build(new CacheLoader<String, User>() {
                @Override
                public User load(String key) {
                    UserDao userDao = new UserDao();
                    return userDao.findById(Integer.valueOf(key));
                }
            });

    public User findById(Integer id) {
        User user = cache.getUnchecked(id.toString()); //cache.get("user:"+id);  与 cache.getUnchecked(id.toString());区别当上面重写方法load（）的时候getUnchecked 部抛异常
        return user;
    }*/


}

缓存使用

    // 发送激活用户账号的邮件,写进去时间,如果没人访问就过期,有人访问就延期时间
    private static Cache<String, String> cache = CacheBuilder
            .newBuilder()
            .expireAfterWrite(6, TimeUnit.HOURS)
            .build();
    // 找回密码token
    private static Cache<String, String> passwordCache = CacheBuilder.newBuilder()
            .expireAfterWrite(30, TimeUnit.MINUTES)
            .build();
    // 限制操作pinlv
    private static Cache<String, String> activeCache = CacheBuilder.newBuilder()
            .expireAfterWrite(30, TimeUnit.SECONDS)
            .build();

测试

/**
 * Created by wanggs on 2017/9/28.
 */
public class CacheTest {
    public static void main(String[] args) {// 限制操作pinlv
        Cache<String, String> activeCache = CacheBuilder.newBuilder()
                .expireAfterWrite(1, TimeUnit.MILLISECONDS)
                .build();
        String id = "1";
        while (true){
            if (activeCache.getIfPresent(id) == null){
                System.out.println("处理业务........***************************..........");
                activeCache.put(id,"000000000");
            }else {
                System.out.println("操作频率太快");
            }
        }


    }
}

转换器：利用 Collections2.transform() 方法来转换集合中的元素。譬如把一个 Set<Integer> 里面所有元素都转换成带格式的 String 来产生新的 Collection<String>:

    @Test
    public void transForm() {
        HashSet<Long> set = Sets.newHashSet();
        set.add(20000000000000L);
        set.add(30000000000000L);
        set.add(40000000000000L);
        List<String> strings = Lists.newArrayList(Collections2.transform(set, new Function<Long, String>() {
            @Override
            public String apply(Long aLong) {
                return String.valueOf(aLong).substring(11);
            }
        }));

        for (String st:strings){
            System.out.println(st);
        }
    }