正则表达式替换字符串中的所有字符

Question

I need regular expression to replace all matching characters except the first one in a squence in string. 我需要正则表达式来替换除字符串中的第一个字符之外的所有匹配字符。

For example; 例如;

For matching with 'A' and replacing with 'B' 用于与'A'匹配并用'B'替换

For matching with ' ' and replacing with 'X' 用于与''匹配并替换为'X'

'[space][space][space]A[space][space][space]' should be replaced with '[space]XXA[space]XX' '[space] [space] [space] A [space] [space] [space]'应替换为'[space] XXA [space] XX'

Answer 1

You need to use this regex for replacement: 您需要使用此正则表达式进行替换：

\\BA

\\B (between word characters) assert position where \\b (word boundary) doesn't match \\B （单词字符之间）断言\\b （字边界）不匹配的位置
A matches the character A literally A字符匹配A字面上

Java Code: Java代码：

String repl = input.replaceAll("\\BA", "B");

UPDATE For second part of your question use this regex for replacement: 更新对于问题的第二部分，请使用此正则表达式进行替换：

"(?<!^|\\w) "

Code: 码：

String repl = input.replaceAll("(?<!^|\\w) ", "X");

Answer 2

Negative Lookbehind and Beginning of String Anchor 负面观察和弦锚的开始

Use the regex (?<!^| )A like this: 使用正则表达式(?<!^| )A如下：

String resultString = subjectString.replaceAll("(?<!^| )A", "B");

In the demo , inspect the substitutions at the bottom. 在演示中，检查底部的替换。

Explanation 说明

(?<!^| ) asserts that what immediately precedes the position is neither the beginning of the string nor a space character (?<!^| )断言紧接在该位置之前的内容既不是字符串的开头也不是空格字符
A matches A A匹配A

Reference 参考