java - 尝试理解和重现正则表达式模式

Question

我目前正在尝试进一步了解模式和匹配器，并发现了以下代码:

private static final Pattern PATTERN = Pattern.compile(
            String.format("addPart%s(?<assembly>%s)\\+(?<amount>%s)%s(?<part>%s)",
                    InOutputStrings.COMMAND_SEPARATOR,
                    InOutputStrings.NAME_PATTERN,
                    InOutputStrings.NUMBER_PATTERN,
                    InOutputStrings.INNER_SEPARATOR,
                    InOutputStrings.NAME_PATTERN));

    private String assemblyName;
    private int amount;
    private String partName;

    ...

    assemblyName = matcher.group("assembly");
    amount = tryParse(matcher.group("amount"));
    partName = matcher.group("part");

据此

    NAME_PATTERN("[a-zA-Z]+"),
    NUMBER_PATTERN("(?!(0[0-9]))[0-9]+"),
    COMMAND_SEPARATOR(" "),
    ARGUMENT_SEPARATOR(";"),
    INNER_SEPARATOR(":")

这里的有效输入是什么？

有人可以告诉我输入模式的样子

“add track <startPoint> -> <endPoint>”？

我正在研究命令行模式，这将是实现输入解析的好方法。

另外，"?", "\\+" and "<assembly>"...是什么意思？ ？

Answer 1

What would be a valid input here?

addPart foo+42:bar

...how this would look like for the input-pattern...

add track (?<startPoint>[a-zA-Z]+) -> (?<endPoint>[a-zA-Z]+)

...what is the meaning of...

• ?!是 Negative Lookahead
• ?<assembly>是 Named Capturing Group
• \\+是一个文字加号(不是正则表达式运算符)

另请注意 %s是 String.format 的变量引用。它也不是正则表达式运算符。