lambda过滤空值、转字符串

List<String> tagsList = Arrays.asList("a", "b", null);
//过滤掉空值
List<String> listWithoutNulls = tagsList.stream()
        .filter(Objects::nonNull)
        .collect(Collectors.toList());
//过滤空值而且逗号分隔转字符串
String tags = tagsList.stream()
        .filter(Objects::nonNull)
        .collect(Collectors.joining(","));
System.out.println(tags);
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