仅用于数字的 Java 正则表达式

Question

Im working on a personal custom text editor for mysql and this is my issue:

This is what im currently using, it will highlight any number, i want to exclude numbers directly concatenated to any letter [A-Za-z], any other symbol is not important since some of them are aritmetic symbols.

private static final String NUMBER_PATTERN = "[0-9]+";

Answer 1

Use this regex to select only numbers that aren't connected to any text

\b\d+\b

• \\d+ allows any number of digits
• \\b at the start and the end defines a word boundary so that it doesn't match words like text12 , 9gag , 4chan etc

Demo: https://regex101.com/r/Fzm2PS/2

// Will match 12, 34, 
// Will not match text12, string, 9gag

Answer 2

What you want is a "positive look-behind" construct in your REGEX.

"[0-9]+(?<=[a-zA-Z])"

Matches:

the 9 in "a9"; 
the 10 in "B10"; 
the 9 in "a9A"

Doesn't Match:

the 9 in "9A"; 
the 10 in "+10"
the 10 in " 10"

Answer 3

Java Regular Expression for only numbers is

String regex=". [az]. " // (after the each dot there is *) and then use variable.matches(regex), it will return true if it contains az and false if it contains only numbers