guava处理字符串与List/Map之间的转换

喜欢ヅ旅行 2022-06-05 02:28 651阅读 0赞

## Guava 是什么? ##

Guava是一种基于开源的Java库，其中包含谷歌正在由他们很多项目使用的很多核心库。这个库是为了方便编码，并减少编码错误。这个库提供用于集合，缓存，支持原语，并发性，常见注解，字符串处理，I/O和验证的实用方法。

## Guava的好处 ##

*  标准化 - Guava库是由谷歌托管。
 *  高效 - 可靠，快速和有效的扩展JAVA标准库
 *  优化 -Guava库经过高度的优化。

函数式编程 -增加JAVA功能和处理能力。

实用程序 - 提供了经常需要在应用程序开发的许多实用程序类。

验证 -提供标准的故障安全验证机制。

最佳实践 - 强调最佳的做法。

关于guava的使用提供一个教程：http://www.yiibai.com/guava/[点击guava教程][guava]

下面我们实现如下的代码片段：guava处理字符串与List/map之间的转换。

Java代码：

package org.zwc.guavatest;
    
    
    import com.google.common.base.Joiner;
    import com.google.common.base.Splitter;
    import com.google.common.collect.Lists;
    import com.google.common.collect.Maps;
    
    import java.util.List;
    import java.util.Map;
    
    /**
     * Created by zhangwenchao on 2017/11/15.
     */
    
    public class GuavaTest {
    
        /**
         * list转换为字符串
         */
    
        public void joinTest(){
            List<String> names = Lists.newArrayList("John", "Jane", "Adam", "Tom");
            String result = Joiner.on(",").join(names);
            System.out.println(result.equals( "John,Jane,Adam,Tom"));
        }
    
    
        /**
         * map转换为字符串
         */
    
        public void whenConvertMapToString_thenConverted() {
            Map<String, Integer> salary = Maps.newHashMap();
            salary.put("John", 1000);
            salary.put("Jane", 1500);
            String result = Joiner.on(" , ").withKeyValueSeparator(" = ")
                    .join(salary);
            System.out.println(result);
        }
    
        /**
         * list转String，跳过null
         */
    
        public void whenConvertListToStringAndSkipNull_thenConverted() {
            List<String> names = Lists.newArrayList("John", null, "Jane", "Adam", "Tom");
            String result = Joiner.on(",").skipNulls().join(names);
            System.out.println(result);
            System.out.println(result.equals( "John,Jane,Adam,Tom"));
        }
    
        /**
         * list转String，将null变成其他值
         */
    
        public void whenUseForNull_thenUsed() {
            List<String> names = Lists.newArrayList("John", null, "Jane", "Adam", "Tom");
            String result = Joiner.on(",").useForNull("nameless").join(names);
            System.out.println(result);
    
    
            System.out.println(result.equals( "John,nameless,Jane,Adam,Tom"));
        }
    
        /**
         * String to List
         */
    
        public void whenCreateListFromString_thenCreated() {
            String input = "apple - banana - orange";
            List<String> result = Splitter.on("-").trimResults().splitToList(input);
            System.out.println(result);
    
        }
    
        /**
         * String to Map
         */
    
        public void whenCreateMapFromString_thenCreated() {
            String input = "John=first,Adam=second";
            Map<String, String> result = Splitter.on(",")
                    .withKeyValueSeparator("=")
                    .split(input);
            System.out.println("first= "+result.get("John"));
            System.out.println("second= "+ result.get("Adam"));
        }
    
        /**
         * 多个字符进行分割
         */
    
        public void whenSplitStringOnMultipleSeparator_thenSplit() {
            String input = "apple.banana,,orange,,.";
            List<String> result = Splitter.onPattern("[.|,]")
                    .omitEmptyStrings()
                    .splitToList(input);
            System.out.println(result);
        }
    
        /**
         * 每隔多少字符进行分割
         */
    
        public void whenSplitStringOnSpecificLength_thenSplit() {
            String input = "Hello world";
            List<String> result = Splitter.fixedLength(3).splitToList(input);
            System.out.println(result);
        }
    
        /**
         * 限制分割多少字后停止
         */
    
        public void whenLimitSplitting_thenLimited() {
            String input = "a,b,c,d,e";
            List<String> result = Splitter.on(",")
                    .limit(4)
                    .splitToList(input);
    
            System.out.println(4==result.size());
            System.out.println(result);
        }
    
    
        public static void main(String[] args) {
            GuavaTest guavaTest = new GuavaTest();
    
            guavaTest.joinTest();
            guavaTest.whenConvertMapToString_thenConverted();
            guavaTest.whenConvertListToStringAndSkipNull_thenConverted();
            guavaTest.whenUseForNull_thenUsed();
            guavaTest.whenCreateListFromString_thenCreated();
            guavaTest.whenCreateMapFromString_thenCreated();
            guavaTest.whenSplitStringOnMultipleSeparator_thenSplit();
            guavaTest.whenSplitStringOnSpecificLength_thenSplit();
            guavaTest.whenLimitSplitting_thenLimited();
    
        }
    
    
    
    
    }

运行结果：

true
    Jane = 1500 , John = 1000
    John,Jane,Adam,Tom
    true
    John,nameless,Jane,Adam,Tom
    true
    [apple, banana, orange]
    first= first
    second= second
    [apple, banana, orange]
    [Hel, lo , wor, ld]
    true
    [a, b, c, d,e]

[guava]: http://www.yiibai.com/guava/