Guava ---- Maps

来源：互联网发布：淘宝访问受限编辑：程序博客网时间：2024/05/21 15:07

本文介绍了Guava集合类Maps、BiMap、ArrayListMultimap相关的使用，比如将具有唯一主键的对象快速存入Map、键值对反转等...

一、对Maps集合类使用案例：

package com.wenniuwuren.guava;import java.util.List;import java.util.Map;import java.util.NavigableMap;import java.util.Set;import com.google.common.base.Function;import com.google.common.collect.Lists;import com.google.common.collect.Maps;import com.google.common.collect.Sets;/** *  * @ClassName: MapsTest  * @Description: Maps集合类扩展使用  * @author wenniuwuren  * @date 2015-6-1 下午5:23:22  * */public class MapsTest {@SuppressWarnings("unchecked")public static void main(String[] args) {Person p1 = new Person("001", "zhang_san");Person p2 = new Person("002", "li_si");List<Person> personList = Lists.newArrayList();personList.add(p1);personList.add(p2);// 将主键当作Map的KeyMap<String, Person> personMap = Maps.uniqueIndex(personList.iterator(), new Function<Person, String>() {@Overridepublic String apply(Person input) {return input.getId();}});System.out.println("将主键当作Map的Key:" + personMap);// 可以说是Maps.uniqueIndex相反的作用Set<Person> personSet = Sets.newHashSet(p1, p2);@SuppressWarnings("unused")Map<Person, String> personAsMap= Maps.asMap(personSet, new Function() {@Overridepublic Object apply(Object input) {return ((Person)input).getId();}});System.out.println(personAsMap);// 转换Map中的value值Map<String, String> transformValuesMap = Maps.transformValues(personMap, new Function<Person, String>() {@Overridepublic String apply(Person input) {return input.getName();}});System.out.println("转换Map中的value值" + transformValuesMap);}}class Person {private String Id;private String name;public Person(String Id, String name) {this.Id = Id;this.name = name;}public String getId() {return Id;}public void setId(String id) {Id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}}

二、对ArrayListMultiMap的使用案例：

package com.wenniuwuren.guava;import java.util.List;import com.google.common.collect.ArrayListMultimap;import com.google.common.collect.HashMultimap;import com.google.common.collect.Lists;/** *  * @ClassName: ArrayListMultiMapTest  * @Description: 一key对应多value  * @author wenniuwuren  * @date 2015-6-1 下午6:17:00  * */public class ArrayListMultiMapTest {public static void main(String[] args) {/** * ArrayListMultimap  List允许重复， 所以大小为4 */ArrayListMultimap<String,String> multiMap = ArrayListMultimap.create();multiMap.put("Foo","1");multiMap.put("Foo","2");multiMap.put("Foo","3");multiMap.put("Foo","3");System.out.println("内容：" + multiMap + " ， 大小：" + multiMap.size());/** * HashMultimap Hash不允许重复值， 大小为3 */HashMultimap<String,String> hashMultiMap =  HashMultimap.create();hashMultiMap.put("Bar","1");hashMultiMap.put("Bar","2");hashMultiMap.put("Bar","3");hashMultiMap.put("Bar","3");hashMultiMap.put("Bar","3");System.out.println("内容：" + hashMultiMap + " ， 大小：" + hashMultiMap.size());}}

三、对BiMaps使用案例：

package com.wenniuwuren.collections;import com.google.common.collect.BiMap;import com.google.common.collect.HashBiMap;/** * 对BiMap工具类的使用： key和value都是唯一的 * @author wenniuwuren * */public class BiMapTest {public static void main(String[] args) {BiMap<String,String> biMap = HashBiMap.create();biMap.put("1","Tom");biMap.put("2","Jerry");// 放入重复值value  将会报错// biMap.put("2","Tom");// 相同Value覆盖前一个//biMap.forcePut("2","Tom");System.out.println(biMap);// key value反转 System.out.println(biMap.inverse());}}

参考资料：

《Getting Started with Google Guava》

2 0