Guava的Joiner和Splitter

导入maven依赖

 <dependency>
            <groupId>com.google.guavagroupId>
            <artifactId>guavaartifactId>
            <version>21.0version>
        dependency>

使用实例

Joiner : 把list或者map转成string

public static void main(String[] args) {
        //join, 
        List<String> stringList = Arrays.asList("1", "2", "4");
        String result = Joiner.on('#').join(stringList);
        System.out.println(result);   //1#2#4

        //过滤掉null值, 
        List<String> stringList2 = Arrays.asList("1", "2", "4", null);
        result = Joiner.on('$').skipNulls().join(stringList2);
        System.out.println(result);  //1$2$4

        //用默认字符替换null，结果=1$2$4$Y
        result = Joiner.on('$').useForNull("Y").join(stringList2);
        System.out.println(result);//1$2$4$Y


        //append to, 返回指定的stringBuilder 
        StringBuilder stringBuilder = new StringBuilder();
        StringBuilder stringBuilder1 = Joiner.on('%').appendTo(stringBuilder, stringList);
        System.out.println(stringBuilder == stringBuilder1); //true


        //java8的实现
        String string = stringList2.stream().filter(s -> s != null).collect(joining("#"));
        System.out.println(string);


        //map的join
        Map<String, String> map = new HashMap<>();
        map.put("1", "2");
        map.put("2", "4");
        //key和value使用=分隔，两个对象之间使用$分隔
        String s = Joiner.on("$").withKeyValueSeparator("=").join(map);
        System.out.println(s);//1=2$2=4
    }

Splitter: 把string转化为list或者map

        //Splitter
        String s1 = "1%2%3%4%6%7";
        List<String> strings = Splitter.on('%').splitToList(s1);
        System.out.println(strings.toString());//[1, 2, 3, 4, 6, 7]
        //去掉空格
        strings = Splitter.on("$").omitEmptyStrings().splitToList("4 $$ e");
        System.out.println(strings.toString());//[4 ,  e]

        //string进行trim
        strings = Splitter.on("$").trimResults().omitEmptyStrings().splitToList("4 $$ e");
        System.out.println(strings.toString());//[4, e]

        //固定长度split
        strings = Splitter.fixedLength(4).splitToList("aaaabbbbccccdddd");
        System.out.println(strings.toString());//[aaaa, bbbb, cccc, dddd]

        //限制分隔出来的list的大小
        strings = Splitter.on("#").limit(3).splitToList("hello#worled#rerere#retrtrtr");
        System.out.println(strings.toString());//[hello, worled, rerere#retrtrtr]


        //正则表达式进行分隔
        strings = Splitter.onPattern("\\|").trimResults().omitEmptyStrings().splitToList("hello|world|3444");
        System.out.println(strings);//[hello, world, 3444]


        //string转map
        Map<String, String> map1 = Splitter.on("%").trimResults()
                .omitEmptyStrings().withKeyValueSeparator("=").split("hello=3%world=4");
        System.out.println(map1);//{hello=3, world=4}