Google Guava 实战之Lists篇

一时失言乱红尘 2023-02-13 03:45 8阅读 0赞

<dependency>
         <groupId>com.google.guava</groupId>
         <artifactId>guava</artifactId>
         <version>27.0.1-jre</version>
     </dependency>
     <dependency>
         <groupId>org.projectlombok</groupId>
         <artifactId>lombok</artifactId>
     </dependency>

package com.lucifer.guava.collections;
    
    import com.google.common.base.Function;
    import com.google.common.collect.ImmutableList;
    import com.google.common.collect.Lists;
    import lombok.AllArgsConstructor;
    import lombok.Data;
    import org.checkerframework.checker.nullness.qual.Nullable;
    
    import java.util.ArrayList;
    import java.util.List;
    
    /**
     * author: lucifer
     * date: 2020/5/27 10:20
     * description: TODO
     */
    public class test4 {
    
        public static void main(String[] args) {
            List<User1> users1 = new ArrayList<>();
            users1.add(new User1("a", 20));
            users1.add(new User1("b", 21));
            users1.add(new User1("c", 22));
    
            List<Integer> list = new ArrayList<>();
            list.add(1);
            list.add(2);
            /**
             * 1、cartesianProduct
             * Lists.cartesianProduct:通过从每个给定列表中依次选择一个元素，返回可以形成的所有可能列表；列表的“ n元笛卡尔积 ”。
             */
            List<List<Object>> cartesianProduct = Lists.cartesianProduct(users1, list);
            System.out.println("Lists.cartesianProduct:===============cartesianProduct:" + cartesianProduct);
            /**
             * 	2、reverse(List<T> list)
             * 返回指定列表的反向视图。
             */
            List<Integer> reverse = Lists.reverse(list);
            System.out.println("Lists.reverse=============revers:" + reverse);
            /**
             * 3、transform(List<F> fromList, Function<? super F,? extends T> function)
             * 返回适用function于的每个元素的列表fromList。
             */
            List<Object> transform = Lists.transform(users1, new Function<User1, Object>() {
                @Nullable
                @Override
                public Object apply(@Nullable User1 user) {
                    return user.getUserName();
                }
            });
            System.out.println("Lists.transform:================transform:" + transform);
            /**
             * 4、partition(List, int)
             * 把List按指定大小分割
             */
            List<List<User1>> partition = Lists.partition(users1, 2);
            System.out.println("Lists.partition:===========partition:" + partition);
            /**
             * 5、Lists.charactersOf(String string)
             * 返回指定字符串的视图作为不可变Character值列表。
             */
            ImmutableList<Character> characters = Lists.charactersOf("张三在学guava");
            System.out.println("Lists.charactersOf(String string)=================="+characters);
            /**
             * 6、Lists.charactersOf(CharSequence sequence)
             *返回指定CharSequence为的List<Character>视图sequence，以Unicode代码单元序列的形式查看 。
             */
            List<Character> characters1 = Lists.charactersOf(new StringBuffer("张三在学guava"));
            System.out.println("Lists.charactersOf(CharSequence sequence)=================="+characters1);
    
        }
    }
    
    @AllArgsConstructor
    @Data
    class User1 {
        private String userName;
        private Integer age;
    }

**控制台打印： **

Lists.cartesianProduct:===============cartesianProduct:[[User1(userName=a, age=20), 1], [User1(userName=a, age=20), 2], [User1(userName=b, age=21), 1], [User1(userName=b, age=21), 2], [User1(userName=c, age=22), 1], [User1(userName=c, age=22), 2]]
    Lists.reverse=============revers:[2, 1]
    Lists.transform:================transform:[a, b, c]
    Lists.partition:===========partition:[[User1(userName=a, age=20), User1(userName=b, age=21)], [User1(userName=c, age=22)]]
    Lists.charactersOf(String string)==================[张, 三, 在, 学, g, u, a, v, a]
    Lists.charactersOf(CharSequence sequence)==================[张, 三, 在, 学, g, u, a, v, a]