Guava collections -- Maps

来源：互联网发布：淘宝二手市场入口编辑：程序博客网时间：2024/06/05 08:31

Guava全文介绍地址:Google Guava
这次主要介绍是的是com.google.common.collect.Maps.主要的作用是就与Java Map相关的静态的实用方法。在Guava中与之类似的还有Sets,Lists以及Queues这些类。
下面就介绍一个Maps的主要用法:

1、准备工作

1.基础类

@Builderpublic class Book {    private String author;    private String title;    private String publisher;    private String isbn;    private double price;}

2.构造数据

public class MapsTest {   private  Book book = new Book.Builder().isbn("ISBN123").title("book1").build();   private  Book book2 = new Book.Builder().isbn("ISBN456").title("book2").build();   private  Book book3 = new Book.Builder().isbn("ISBN789").title("book3").build();   private  List<Book> books = Lists.newArrayList(book,book2,book3);}

2、把集合中唯一Filed作用的Map

    @Test    public void uniqueIndexTest(){        Map<String,Book> bookMap = Maps.uniqueIndex(books,new Function<Book, String>() {            @Override            public String apply(Book book) {                return book.getIsbn();            }        });       assertThat(bookMap.get("ISBN123"),is(book));       assertThat(bookMap.get("ISBN456"),is(book2));       assertThat(bookMap.get("ISBN789"),is(book3));    }

3、把Set中对象作为key,把field作为value

    @Test    public void asMapTest(){        Set<Book> bookSet = Sets.newHashSet(books);        Map<Book,String> bookToIsbn = Maps.asMap(bookSet,new Function<Book, String>() {            @Override            public String apply(Book book) {                return book.getIsbn();            }        });        assertThat(bookToIsbn.get(book),is("ISBN123"));        assertThat(bookToIsbn.get(book2),is("ISBN456"));        assertThat(bookToIsbn.get(book3),is("ISBN789"));    }

4、对Map的Value进行转换

    @Test    public void transformValuesTest(){        Map<String,Book> bookMap = Maps.uniqueIndex(books,new Function<Book, String>() {            @Override            public String apply(Book book) {                return book.getIsbn();            }        });        Map<String,String> map = Maps.transformValues(bookMap,new Function<Book, String>() {            @Override            public String apply(Book book) {                 return book.getTitle();            }        });        assertThat(map.get("ISBN123"),is("book1"));        assertThat(map.get("ISBN456"),is("book2"));        assertThat(map.get("ISBN789"),is("book3"));    }

5、对Map的Entry进行转换

    @Test    public void transformEntriesTest(){        Map<String,Book> bookMap = Maps.uniqueIndex(books,new Function<Book, String>() {            @Override            public String apply(Book book) {                return book.getIsbn();            }        });        Map<String,String> map = Maps.transformEntries(bookMap,new Maps.EntryTransformer<String,Book,String>(){            @Override            public String transformEntry(String key, Book value) {                StringBuilder builder = new StringBuilder();                return builder.append(key).append("|").append(value.getTitle()).toString();            }        });        assertThat(map.get("ISBN123"),is("ISBN123|book1"));        assertThat(map.get("ISBN456"),is("ISBN456|book2"));        assertThat(map.get("ISBN789"),is("ISBN789|book3"));    }

更多功能等待你的发现。

0 0