将字符添加到String的中间

I need your help to turn a String like 12345678 into 1234.56.78

我需要你的帮助把像12345678这样的字符串变成1234.56.78

[FOUR DIGITS].[TWO DIGITS].[TWO DIGITS]

My code:

String s1 = "12345678";
s1 = s1.replaceAll("(\\d{4})(\\d+)", "$1.$2").replaceAll("(\\d{2})(\\d+)", "$1.$2");
System.out.println(s1);

But the result is 12.34.56.78

但结果是12.34.56.78

3 个解决方案

#1

If you are sure that you'll always have the input in the same format then you can simply use a StringBuilder and do something like this:

如果您确定您将始终以相同的格式输入,那么您可以简单地使用StringBuilder并执行以下操作:

String input = "12345678";
String output = new StringBuilder().append(input.substring(0, 4))
        .append(".").append(input.substring(4, 6)).append(".")
        .append(input.substring(6)).toString();
System.out.println(output);

This code creates a new String by appending the dots to the sub-strings at the specified locations.

此代码通过将点附加到指定位置的子字符串来创建新的String。

Output:

1234.56.78

#2

Use a single replaceAll() method with updated regex otherwise the second replaceAll() call will replace including the first four digits.

使用单个replaceAll()方法和更新的正则表达式,否则第二个replaceAll()调用将替换包括前四个数字。

System.out.println(s1.replaceAll("(\\d{4})(\\d{2})(\\d+)", "$1.$2.$3")

#3

This puts dots after every pair of chars, except the first pair:

这会在每对字符之后加上点,第一对除外:

str = str.replaceAll("(^....)|(..)", "$1$2.");

This works for any length string, including odd lengths.

这适用于任何长度的字符串,包括奇数长度。

For example

"1234567890123" --> "1234.56.78.90.12.3"

#1