java-匹配字符串中的正则表达式模式(列出匹配和不匹配的部分)

Question

我有一个包含五个字段的 csv 字符串(3 个必填字段，2 个可选字段)。可选字段位于位置 3 和 5。我有一个正则表达式模式来识别双引号中的字符串

    private static final String TEXT_IN_DBL_QUOTES_REGEX="\"([^\"]*)\"";
    private static final String rowData="\"Field1\", \"Field2\", , \"Field4\", ";

    public static void main(String[] args){
        List<String> fields = Lists.newArrayList();
        Pattern regex = Pattern.compile(TEXT_IN_DBL_QUOTES_REGEX);
        Matcher matcher = regex.matcher(rowData);
        while(matcher.find()){
           fields.add(matcher.group(1));
        }
        return fields;
    }

My expected result is an array list containing 
Field1, Field2, null, Field4, null
but the above is returning 
Field1, Field2, Field4

如何调整上面的代码以获得所需的结果？

Answer 1

您可以像这样调整正则表达式:

String TEXT_IN_DBL_QUOTES_REGEX="\"([^\"]*)\"|(?<=,) *(?=,|$)";
String rowData="\"Field1\", \"Field2\", , \"Field4\", ";

List<String> fields = new ArrayList<>();
Pattern regex = Pattern.compile(TEXT_IN_DBL_QUOTES_REGEX);
Matcher matcher = regex.matcher(rowData);
while(matcher.find()) {
    fields.add(matcher.group(1));
}
System.out.println (fields);

输出:

[Field1, Field2, null, Field4, null]