string.replaceAll 的第一个参数是正则表达式，而不是j一个字符串。左开括号是正则表达式中的特殊字符，因此您必须将其转义：

The first argument to string.replaceAll is a regular expression, not just a string. The opening left bracket is a special character in a regex, so you must escape it:

line.replaceAll("\\(", "_");

或者，因为你要替换一个字符，你可以像这样使用 string.replace ：

Alternatively, since you are replacing a single character, you could use string.replace like so:

line.replace('(', '_');