table of 50 most frequently used regular expressions in Java programs, along with what they typically replace with, and a brief meaning., in java programming.
Here's a table of 50 most frequently used regular expressions in Java programs, along with what they typically replace with, and a brief meaning.
| # | Regular Expression | Replace With | Meaning / Purpose |
|---|---|---|---|
| 1 | \\s+ | " " | Replace multiple whitespaces with a single space |
| 2 | \\s{2,} | " " | Replace 2 or more spaces with one |
| 3 | `^\s+ | \s+$` | "" |
| 4 | \\d+ | "" | Remove all digits |
| 5 | \\D+ | "" | Remove all non-digit characters |
| 6 | \\w+ | "" | Remove all words (alphanumeric + _) |
| 7 | \\W+ | "" | Remove all non-word characters |
| 8 | \\bword\\b | "" | Remove exact word "word" |
| 9 | \\b\\w{1,3}\\b | "" | Remove all short words (1–3 characters) |
| 10 | [a-z] | "" | Remove all lowercase letters |
| 11 | [A-Z] | "" | Remove all uppercase letters |
| 12 | [^a-zA-Z0-9] | "" | Remove special characters |
| 13 | [aeiouAEIOU] | "" | Remove all vowels |
| 14 | \\n | " " | Replace newline with space |
| 15 | \\r?\\n | " " | Normalize line breaks |
| 16 | [ ]{2,} | " " | Remove extra spaces |
| 17 | \\b[tT]\\w*[tT]\\b | "" | Remove words starting & ending with 't'/'T' |
| 18 | (?i)error | "issue" | Replace 'error' (case-insensitive) with 'issue' |
| 19 | http[s]?://\\S+ | "" | Remove URLs |
| 20 | <[^>]*> | "" | Remove HTML tags |
| 21 | \\d{4}-\\d{2}-\\d{2} | "" | Remove dates in YYYY-MM-DD format |
| 22 | \\$\\d+(\\.\\d{2})? | "" | Remove dollar amounts |
| 23 | [A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+ | "***@***.com" | Mask email addresses |
| 24 | (?i)password:\\s*\\S+ | "password: ***" | Mask passwords |
| 25 | \\d{10} | "**********" | Mask 10-digit phone numbers |
| 26 | `(?i)\b(?:yes | no)\b` | "true/false" |
| 27 | \\(.*?\\) | "" | Remove content inside parentheses |
| 28 | \\[.*?\\] | "" | Remove content inside square brackets |
| 29 | "\\s*-\\s*" | "-" | Clean up hyphen spacing |
| 30 | "[^\\x00-\\x7F]" | "" | Remove non-ASCII characters |
| 31 | \\bJava\\b | "JAVA" | Replace exact word 'Java' with uppercase |
| 32 | \\. | "." | Escape dot to literal period |
| 33 | \\* | "" | Remove asterisks |
| 34 | \\+ | "" | Remove plus signs |
| 35 | \\? | "" | Remove question marks |
| 36 | [\"'] | "" | Remove quotes |
| 37 | (?m)^\\s*$ | "" | Remove blank lines |
| 38 | \\s*;\\s* | "; " | Clean up semicolon spacing |
| 39 | ,\\s* | ", " | Normalize commas |
| 40 | `(?i)true | false` | "boolean" |
| 41 | \\d{1,3}(,\\d{3})*(\\.\\d+)? | "" | Remove currency/number with commas |
| 42 | \\b[A-Z]{2,}\\b | "" | Remove all-uppercase words (acronyms) |
| 43 | \\b\\d{1,2}/\\d{1,2}/\\d{2,4}\\b | "" | Remove dates in DD/MM/YYYY or MM/DD/YYYY format |
| 44 | `(?i)\b(?:and | or | but)\b` |
| 45 | (?<=\\().*?(?=\\)) | "" | Remove content between parentheses (keep parentheses) |
| 46 | (?<=\\[).*?(?=\\]) | "" | Remove content between square brackets (keep brackets) |
| 47 | \\b\\d+\\b | "" | Remove standalone numbers |
| 48 | (?<!\\w)\\d{5}(?!\\w) | "ZIP" | Replace 5-digit ZIP code |
| 49 | `(?i)(\bnull\b | \bundefined\b)` | "N/A" |
| 50 | `\s*\ | \s*` | `" |
