正则表达式-匹配重复字符串的模式

Question

I want a pattern to match "+-+-+-+-+-.......",the "+-" can occur as many times,but they should be together...not like"+++--+---"

I tried "[+-]+",but it doesn't specifies that + and - are consecutive

Answer 1

The square brackets ( [] ) specify a character class. What you instead want is to use a non-capturing group:

(?:\+-)+

You can of couse make it a capturing group (\\+-)+ if you want to well capture it all.

Answer 2

Consider the following samples:

+++--+---
-+-+-
-+-+-+
-+-+-+-
------
++++++
+-+-+-
+-+-+-+
+-+-+-+-
--++--++-
++--++--+
+-5
-+-A

Vallentin's pattern has no anchors and will match anything inside the string. (?:\\+-)+

Can the string end on the same character it starts with?

if not, change it to:

^(?:\\+-)+$

if it can:

For "+ only starts": Access full match result using pattern: ^(\\+(?:-|$))+$

For possibility of "+ and - starts": Access full match result using pattern: ^(?:([+-])(?!\\1))+$

Compare all three patterns @ this demo that defaults to Vallentin's pattern .