guava之Lists、Sets、Maps用法

深藏阁楼爱情的钟 2023-05-30 09:25 6阅读 0赞

> guava处理java.util.List的工具类  
> guava处理java.util.Set的工具类  
> guava处理java.util.Map的工具类

## Lists常用方法 ##

package com.me.guava.collect;
    
    import com.google.common.collect.Lists;
    
    import java.util.ArrayList;
    import java.util.List;
    
    /** * @author yanyugang * @description * @date 2019-11-09 11:44 */
    public class ListsTest { 
        public static void main(String[] args){ 
            coreFunList();
        }
    
        // Lists主要方法
        public static void coreFunList(){ 
            System.out.println("---------字符串转集合--------------");
            String str="10010";
            ArrayList<String> list=Lists.newArrayList(str);
            list.forEach(n -> System.out.print(n + " "));
            System.out.println();
            System.out.println("----------数组转集合-------------");
            String[] array={ "1", "2", "3", "4"};
            ArrayList<String> strings=Lists.newArrayList(array);
            strings.forEach(n -> System.out.print(n + " "));
            System.out.println();
            System.out.println("----------数组反转-------------");
            List<String> reverse=Lists.reverse(strings);
            reverse.forEach(n -> System.out.print(n + " "));
            System.out.println();
            System.out.println("----------添加新元素-------------");
            //return an unmodifiable list containing the specified elements
            List<String> addList=Lists.asList("0", array);
            addList.forEach(n -> System.out.print(n + " "));
            System.out.println();
            System.out.println("----------获取子集合-------------");
            //a list of consecutive sublists
            List<List<String>> partition=Lists.partition(addList, 2);
            partition.forEach(n -> System.out.print(n + " "));
            System.out.println();
        }
    }

## Sets常用方法 ##

package com.me.guava.collect;
    
    import com.google.common.collect.Sets;
    
    import java.util.HashSet;
    import java.util.Set;
    
    /** * @author yanyugang * @description * Static utility methods pertaining to {@link Set} instances. * @date 2019-11-09 15:01 */
    public class SetsTest { 
        public static void main(String[] args){ 
            coreFunList();
        }
    
        // Sets主要方法
        public static void coreFunList(){ 
            System.out.println("---------字符串转集合--------------");
            HashSet<String> set1=Sets.newHashSet("1","8");
            set1.forEach(n -> System.out.print(n + " "));
            System.out.println();
            HashSet<String> set2=Sets.newHashSet("1","2");
            set2.forEach(n -> System.out.print(n + " "));
            System.out.println();
            System.out.println("---------set1和set2并集--------------");
            Sets.SetView<String> union=Sets.union(set1, set2);
            union.forEach(n -> System.out.print(n + " "));
            System.out.println();
            System.out.println("---------set1和set2交集--------------");
            Sets.SetView<String> intersection=Sets.intersection(set1, set2);
            intersection.forEach(n -> System.out.print(n + " "));
            System.out.println();
            System.out.println("---------set1和set2差集--------------");
            //差集 1中有而2中没有的
            Sets.SetView<String> difference=Sets.difference(set1, set2);
            difference.forEach(n -> System.out.print(n + " "));
            System.out.println();
            System.out.println("---------set1和set2相对差集--------------");
            //相对差集 1中有2中没有 2中有1中没有的 取出来做结果
            Sets.SetView<String> symmetricDifference=Sets.symmetricDifference(set1, set2);
            symmetricDifference.forEach(n -> System.out.print(n + " "));
            System.out.println();
    
        }
    }

## Maps常用方法 ##

package com.me.guava.collect;
    
    import com.google.common.base.Function;
    import com.google.common.collect.Lists;
    import com.google.common.collect.Maps;
    import com.google.common.collect.Sets;
    
    import java.util.List;
    import java.util.Map;
    import java.util.Set;
    
    /** * @author yanyugang * @description * Static utility methods pertaining to {@link Map} instances * @date 2019-11-09 16:52 */
    public class MapsTest { 
        static Book book=new Book.BookBuilder().isbn("ISBN123").title("book1").build();
        static Book book2=new Book.BookBuilder().isbn("ISBN456").title("book2").build();
        static Book book3=new Book.BookBuilder().isbn("ISBN789").title("book3").build();
        static List<Book> books=Lists.newArrayList(book, book2, book3);
    
    
        public static void main(String[] args){ 
            setToMap();
        }
    
        /** * List 转 Map */
        public static void listToMap(){ 
    
            Map<Object, Book> bookMap=Maps.uniqueIndex(books, book1 -> book1.getIsbn());
    
            bookMap.forEach((key, value) -> { 
                System.out.println(key);
                System.out.println(value.getTitle());
            });
        }
    
        /** * Set 转 Map * Returns a live {@link Map} view whose keys are the contents of {@code set} * and whose values are computed on demand using {@code function}. */
        public static void setToMap(){ 
            Set<Book> bookSet=Sets.newHashSet(books);
            Map<Book, String> bookMap=Maps.asMap(bookSet, input -> input.getIsbn());
            System.out.println(bookMap.size());
            bookMap.forEach((key, value) -> { 
                System.out.println(key.getTitle());
                System.out.println(value);
            });
        }
        
    }

## 教程 ##

*  [Guava教程][Guava]

[Guava]: https://www.yiibai.com/guava