利用apache Collections和google guava对list和map进行过滤和排序

最新推荐文章于 2021-07-06 18:32:56 发布

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最新推荐文章于 2021-07-06 18:32:56 发布

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分类专栏： Java 开源应用文章标签： java

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本文介绍了如何使用Apache Commons和Google Guava库对Java中的List和Map进行过滤和排序操作。通过具体示例展示了如何根据对象属性筛选集合元素，并利用Guava库简化了集合处理流程。

[url]http://www.jiancool.com/article/50723356810/[/url]
在工作中，我们常常需要对List或者Map等集合结果过滤或者排序，这里我通过使用apache commons和google guava中的方法，简单实现了一下，方便以后使用。
例子中使用的是apache commons3.1和google-guava14，最新版本是18
apache项目下载地址：http://projects.apache.org/indexes/quick.html
apache Collectoins下载地址：http://commons.apache.org/proper/commons-collections/

[color=red][b] apache代码如下：[/b][/color]

对List中的对象按不同属性排序，请看此

package com.umapp.test;  

public class UserGuava {  
    private String name;  
    private int age;  
    @Override  
    public int hashCode() {  
        final int prime = 31;  
        int result = 1;  
        result = prime * result + age;  
        result = prime * result + ((name == null) ? 0 : name.hashCode());  
        return result;  
    }  
    @Override  
    public boolean equals(Object obj) {  
        if (this == obj)  
            return true;  
        if (obj == null)  
            return false;  
        if (getClass() != obj.getClass())  
            return false;  
        UserGuava other = (UserGuava) obj;  
        if (age != other.age)  
            return false;  
        if (name == null) {  
            if (other.name != null)  
                return false;  
        } else if (!name.equals(other.name))  
            return false;  
        return true;  
    }  
    public UserGuava(){  

    }  
    public String getName() {  
        return name;  
    }  
    public void setName(String name) {  
        this.name = name;  
    }  
    public int getAge() {  
        return age;  
    }  
    public void setAge(int age) {  
        this.age = age;  
    }  
}

package com.umapp.test;  

import java.util.ArrayList;  
import java.util.Iterator;  
import java.util.List;  

import org.apache.commons.collections.Predicate;  
import org.apache.commons.collections.iterators.FilterIterator;  
import org.apache.commons.collections.iterators.UniqueFilterIterator;  

public class TestApache {  

    /** 
     * @param args 
     */  
    public static void main(String[] args) {  
        List<UserGuava> list = new ArrayList<UserGuava>();  
        UserGuava user = new UserGuava();  
        user.setAge(1);  
        user.setName("Apple");  
        list.add(user);  
        user = new UserGuava();  
        user.setAge(2);  
        user.setName("Facebook");  
        list.add(user);  
        user = new UserGuava();  
        user.setAge(3);  
        user.setName("Twitter");  
        list.add(user);  
        user = new UserGuava();  
        user.setAge(4);  
        user.setName("Youtube");  
        list.add(user);  
        user = new UserGuava();  
        user.setAge(5);  
        user.setName("Telerik");  
        list.add(user);  
        user = new UserGuava();  
        user.setAge(6);  
        user.setName("Google");  
        list.add(user);  
        user = new UserGuava();  
        user.setAge(6);  
        user.setName("Google");  
        list.add(user);  
        Predicate predicate=new Predicate(){             
            @Override  
            public boolean evaluate(Object arg0) {  
                UserGuava u = (UserGuava)arg0;  
                return u.getAge()>2;  
            }  
        };  
        Iterator<?> iterator=new FilterIterator(list.iterator(),predicate);  
        while(iterator.hasNext()){  
            UserGuava u = (UserGuava)iterator.next();  
            System.out.println(u.getName()+","+u.getAge());  
        }  
        System.out.println("-------------------你懂的------------------------");  
        Iterator iterator1=new UniqueFilterIterator(list.iterator());  
        while(iterator1.hasNext()){  
            UserGuava u = (UserGuava)iterator1.next();  
            System.out.println(u.getName()+","+u.getAge());  
        }  
    }  

}

打印结果：

Twitter,3

Youtube,4

Telerik,5

Google,6

Google,6

-------------------你懂的------------------------

Apple,1

Facebook,2

Twitter,3

Youtube,4

Telerik,5

Google,6

[color=red][b] google guava代码： [/b][/color]

package com.umapp.test;  

import java.util.Comparator;  

public class NameComparator implements Comparator<UserGuava> {  
    @Override  
    public int compare(UserGuava user, UserGuava user1) {  
        return user.getName().compareTo(user1.getName());  
    }  
}

package com.umapp.test;  

import java.util.Comparator;  

public class AgeComparator implements Comparator<UserGuava> {  
    @Override  
    public int compare(UserGuava user, UserGuava user1) {  
        return user.getAge() > user1.getAge() ? 1 : (user.getAge() == user1.getAge() ? 0 : -1);  
    }  
}

package com.umapp.test;  

import java.util.Collection;  
import java.util.Collections;  
import java.util.Comparator;  
import java.util.List;  
import java.util.Map;  
import java.util.Map.Entry;  
import java.util.Objects;  

import com.google.common.base.Predicate;  
import com.google.common.base.Predicates;  
import com.google.common.collect.Collections2;  
import com.google.common.collect.Lists;  
import com.google.common.collect.Maps;  
import com.google.common.collect.Ordering;  

public class TestGuava {  

    public static void main(String[] args) {  
        Map<String, UserGuava> map = Maps.newHashMap();  
        List<UserGuava> list = Lists.newArrayList();  
        UserGuava user = new UserGuava();  
        user.setAge(1);  
        user.setName("JetBrains");  
        map.put("1", user);  
        list.add(user);  
        user = new UserGuava();  
        user.setAge(2);  
        user.setName("Apple");  
        list.add(user);  
        map.put("2", user);  
        user = new UserGuava();  
        user.setAge(3);  
        user.setName("Telerik");  
        list.add(user);  
        map.put("3", user);  
        user = new UserGuava();  
        user.setAge(4);  
        user.setName("Google");  
        list.add(user);  
        map.put("4", user);  
        user = new UserGuava();  
        user.setAge(5);  
        user.setName("Twitter");  
        list.add(user);  
        map.put("5", user);  
        user = new UserGuava();  
        user.setAge(2);  
        user.setName("Facebook");  
        list.add(user);  
        map.put("2", user);  
        user = new UserGuava();  
        user.setAge(1);  
        user.setName("Youtube");  
        map.put("1", user);  
        list.add(user);  
        Predicate<UserGuava> preFilter = new Predicate<UserGuava>(){  
            @Override  
            public boolean apply(UserGuava user) {  
                return user.getAge()>2;  
            }  
        };  
        for (Entry<String, UserGuava> e : map.entrySet()) {  
            if (preFilter.apply(e.getValue())) {  
                UserGuava u= (UserGuava)e.getValue();  
                System.out.println("Map-UserGuava="+u.getName()+","+u.getAge());  
            }  
        }  
        System.out.println("-------------------你懂的------------------------");  
        for (UserGuava u:list) {  
            if (preFilter.apply(u)) {  
                System.out.println("List-UserGuava="+u.getName()+","+u.getAge());  
            }  
        }  
        System.out.println("-------------------你懂的------------------------");  
        Predicate<UserGuava> p1 = new Predicate<UserGuava> () {    
            @Override    
            public boolean apply(UserGuava user) {    
                if (user == null) {    
                    return false;    
                }    
                if (Objects.equals(user.getAge(), 1)) {    
                    return false;    
                }    
                return true;    
            }    
        };  
        Predicate<UserGuava> p2 = new Predicate<UserGuava> () {    
            @Override    
            public boolean apply(UserGuava user) {    
                if (user == null) {    
                    return false;    
                }    
                if (Objects.equals(user.getAge(), 2)) {    
                    return false;    
                }    
                return true;    
            }    
        };  
        Predicate<UserGuava> unionPredicate = Predicates.and(p1, p2);    
            //两种处理方式  
       // List<UserGuava> newUserList = Lists.newArrayList(Iterators.filter(list.iterator(), unionPredicate));  
        Collection<UserGuava> newUserList =(Collection<UserGuava>) Collections2.filter(list, unionPredicate);  
        for (UserGuava u:newUserList) {  
            System.out.println("List-IN-UserGuava="+u.getName()+","+u.getAge());  
        }  
        System.out.println("-------------------你懂的------------------------");  
            //先按年龄，再按名称排序  
        Comparator<UserGuava> userComparator = Ordering  
                .from(new AgeComparator()).compound(new NameComparator());  

        Collections.sort(list, userComparator);  
        for (UserGuava u:list) {  
            System.out.println("List-Sort-UserGuava="+u.getName()+","+u.getAge());  
        }  
    }  

}

打印结果：

Map-UserGuava=Telerik,3

Map-UserGuava=Twitter,5

Map-UserGuava=Google,4

-------------------你懂的------------------------

List-UserGuava=Telerik,3

List-UserGuava=Google,4

List-UserGuava=Twitter,5

-------------------你懂的------------------------

List-IN-UserGuava=Telerik,3

List-IN-UserGuava=Google,4

List-IN-UserGuava=Twitter,5

-------------------你懂的------------------------

List-Sort-UserGuava=JetBrains,1

List-Sort-UserGuava=Youtube,1

List-Sort-UserGuava=Apple,2

List-Sort-UserGuava=Facebook,2

List-Sort-UserGuava=Telerik,3

List-Sort-UserGuava=Google,4

List-Sort-UserGuava=Twitter,5