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

ゝ一世哀愁。 2022-05-08 08:52 174阅读 0赞

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/][http_commons.apache.org_proper_commons-collections]

apache代码如下：

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

google guava代码：

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

[http_commons.apache.org_proper_commons-collections]: http://commons.apache.org/proper/commons-collections/