java - Understanding `+` in regular expression -

i have regular expression remove usernames tweets. looks this:

regexfinder = "(?:\\s|\\a)[@]+([a-za-z0-9-_]+):"; 

i'm trying understand each component does. far, i've got:

(       used begin “group” element ?:      starts non-capturing group (this means 1 removed final result) \\s     matches against shorthand characters |       or \\a     matches @ start of string , matches position opposed character [@]     matches against symbol (which used twitter usernames) +       match previous followed ([a-za-z0-9- ]  match against capital or small characters , numbers or hyphens 

i'm bit lost last bit though. tell me +): means? i'm assuming bracket ending group, don't colon or plus sign.

if i've made mistakes in understanding of regex please feel free point out!

the + means "one or more" of whatever follows.

in case [@]+ means "one or more @ symbols" , [a-za-z0-9-_]+ means "one or more of letter, number, dash, or underscore". + 1 of several quantifiers, learn more here.

the colon @ end making sure match has colon @ end of match.

sometimes helps see visualization, here 1 generated debuggex: