[英]Replacing some but not all occurrences of a char in Java String
I am learning Java, and in a task I have to replace some but not all occurrences of a '-' to a '(' and same for '*' a ')', only if the inside of the - is an id as as follows:我正在学习Java,并且在一项任务中,我必须将一些但不是所有出现的“-”替换为“(”,并且对于“*”和“)”也是如此,前提是 - 的内部是一个 id 为如下:
String input = "-id1234* -id1235* -id1236* Do not replace these -signs*";
String output = "(id1234) (id1235) (id1236) Do not replace these -signs*";
I have tried iterating through a loop, and replacing the first occurrence once the for loop goes to a position with i
, but that doesn't seem to work:我尝试遍历一个循环,并在 for 循环到达
i
位置后替换第一次出现,但这似乎不起作用:
static String clean(String input) {
String tmp = input;
for (int i = 0; i < input.length(); i++) {
if (input.charAt(i) == 'i') {
tmp = input.replaceFirst("-", "(");
} else if(Character.isDigit(i)){
tmp = input.replaceFirst("*", ")");
}
}
return tmp;
}
You didn't say how your method doesn't seem to work, but it looks like you are replacing "*" with ")" for every digit you find: the 1, the 2, the 3, the 4, then the 1, 2, 3, 5, so that many more end parentheses replace asterisks than you expect.你没有说你的方法似乎不起作用,但看起来你正在用“)”替换你找到的每个数字:1、2、3、4,然后是 1 , 2, 3, 5,所以用更多的括号代替星号。
This assumes that "id" followed by numbers is always what you want to match in between the "-" and the "*".这假定后跟数字的“id”始终是您想要在“-”和“*”之间匹配的内容。 Use a regular expression to match and replace with the
replaceAll
method :使用正则表达式匹配并替换为
replaceAll
方法:
return input.replaceAll("-(id\\d+)\\*", "($1)");
Match a -
.匹配一个
-
。 Form a capturing group in your regular expression with parentheses.用括号在正则表达式中形成一个捕获组。 Match
id
.匹配
id
。 Match one or more digits consecutively.连续匹配一个或多个数字。 After the capturing group, match a
*
.在捕获组之后,匹配一个
*
。 The backslashes are for 1) escaping a literal backslash to form the character class \d - digits, and 2) escaping a literal backslash to regex-escape the asterisk.反斜杠用于 1) 转义文字反斜杠以形成字符类 \d - 数字,以及 2) 转义文字反斜杠以正则表达式转义星号。
The $1
inside the replacement expression means the first capturing group.替换表达式中的
$1
表示第一个捕获组。
Output:输出:
(id1234) (id1235) (id1236) Do not replace these -signs*
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