public class JoinerTest {

    private static final List<String> list1 = Arrays.asList

                ("google","guava","java","scala","kafka");

    private static final List<String> list2 = Arrays.asList

            ("google","guava","java",null,"scala","kafka");

    public static void main(String[] args) throws IOException {

        //1.用指定的字符连接

        String join = Joiner.on("#").join(list1);

        System.out.println("用 # 号连接的字符串是："+join);

        //2.跳过连接中的null值

        String joinNull = Joiner.on("#").skipNulls().join(list2);

        System.out.println("用 # 号连接的字符串,跳过中间的null值："+joinNull);

        //3.有null值存在时用指定值代替

        String joinUseForNull = Joiner.on("#").useForNull("DEFAULT").join(list2);

        System.out.println("用指定值代替集合中的null值："+joinUseForNull);

        //4.把集合变成一个stringBuilder 或者stringBuffer

        StringBuilder builder = Joiner.on("#").useForNull("DEFAULT").appendTo(new StringBuilder(), list2);

        StringBuffer buffer = Joiner.on("#").useForNull("DEFAULT").appendTo(new StringBuffer(), list2);

        System.out.println("拼接成的 builder是："+builder);

        System.out.println("拼接成的buffer是："+buffer);

        //5.对于map中key value的分隔

        Map<String, String> map = new HashMap<String, String>();

        map.put("hello", "java");

        map.put("scala", "guava");

        String joinMap = Joiner.on("#").withKeyValueSeparator("=").join(map);

        System.out.println("key value 的分隔符："+joinMap);

    }

}
//打印结果

用 # 号连接的字符串,跳过中间的null值：google#guava#java#scala#kafka
用指定值代替集合中的null值:google#guava#java#DEFAULT#scala#kafka
拼接成的 builder是：google#guava#java#DEFAULT#scala#kafka
拼接成的buffer是：google#guava#java#DEFAULT#scala#kafka
key value 的分隔符：scala=guava#hello=java