Guava：google公司开发的一款Java类库扩展工具包

Guava是google公司开发的一款Java类库扩展工具包

文档

• https://github.com/google/guava
• https://github.com/google/guava/wiki
• https://guava.dev/releases/snapshot-jre/api/docs/
• https://mvnrepository.com/artifact/com.google.guava/guava

maven 依赖

<dependency> <groupId>com.google.guava</groupId> <artifactId>guava</artifactId> <version>31.1-jre</version> </dependency>

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示例1：连接字符串

package com.example; import com.google.common.base.Joiner; import java.util.Arrays; public class Demo { public static void main(String[] args) { // JDK 1.8 String var1 = String.join("-", Arrays.asList("A", null, "C", "D")); System.out.println(var1); // A-null-C-D // guava Joiner joiner = Joiner.on("-").skipNulls(); String var2 = joiner.join("A", null, "C", "D"); System.out.println(var2); // A-C-D } }

示例2：统计元素出现次数

package com.example; import com.google.common.collect.HashMultiset; import com.google.common.collect.Multiset; import java.util.Arrays; public class Demo { public static void main(String[] args) { String[] words = {"A", "B", "C", "B"}; // JDK 1.8 Map<String, Integer> counts = new HashMap<String, Integer>(); for (String word : words) { Integer count = counts.get(word); if (count == null) { counts.put(word, 1); } else { counts.put(word, count + 1); } } System.out.println(counts); // {A=1, B=2, C=1} // guava Multiset<String> multiset = HashMultiset.create(); multiset.addAll(Arrays.asList(words)); System.out.println(multiset); // [A, B x 2, C] System.out.println(multiset.count("B")); // 2 } }

示例3：key对应集合

package com.example; import com.google.common.collect.ArrayListMultimap; import com.google.common.collect.Multimap; public class Demo { public static void main(String[] args) { Multimap<String, Integer> multimap = ArrayListMultimap.create(); multimap.put("A", 1); multimap.put("A", 2); multimap.put("B", 4); multimap.put("C", 5); System.out.println(multimap); // {A=[1, 2], B=[4], C=[5]} } }

参考 Guava中这些Map的骚操作，让我的代码量减少了50% 一篇让你熟练掌握Google Guava包(全网最全)