Java String remove all non numeric characters but keep the decimal separator

When digits become the story plot

Say you want to fish out entire decimal numbers, not just purging alphabets. Watch the regex magic unfold:

String input = "a12.334tyz0.78x";
Pattern pattern = Pattern.compile("(\\d+\\.\\d+)");  // Fishing net for decimals
Matcher matcher = pattern.matcher(input);   // Time to fish!
StringBuilder result = new StringBuilder();
while (matcher.find()) {
    result.append(matcher.group()).append(" ");  // Gotcha decimal!
}
// The end result: a happy string holding "12.334 0.78 "!
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In this cine-regex movie, we are on a mission to locate digits separated by a decimal point and take them hostage, whole and unscattered.

Best Practice: User Manual for regex

While regex is like a superhero in the world of text manipulation, with great power comes great responsibility. Use it wisely and judiciously:

• Capture groups ( ): Great for extracting info, but frequent use may complicate your regex. Keep it simple, sweetheart!
• Negation [^ ] and inclusion [ ]: Excellent for specifying what you don't or do want. Cherry-pick like a pro!
• Lookaheads (?= ) and lookbehinds (?<= ): Advanced constructs for conditional matching. Use them, but don't abuse them!
• Performance: They say slow and steady wins the race, but not when you have huge string operations awaiting. Learn regex optimization!

Let's juggle with special cases

Dealing with negatives

Negatives getting ignored? Include them in your regex guest list:

String sanitized = "abc-123.45xyz".replaceAll("[^-\\d.]+", "");
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[^-\\d.] essentially tells regex to keep the party going with negatives besides digits and points.

Retaining more than decimals

And if decimals have companions - dashes, welcome them too:

String sanitized = "abc-123.45xyz".replaceAll("[^\\d.-]+", "");
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While dashes are party-poopers with ranges in regex, give them a corner spot by placing them at the beginning or end of the character class.

Making regex less intimidating

For those who find the regex party rough, there are friendlier options like CharMatcher from Google's Guava library:

String sanitized = CharMatcher.inRange('0', '9').or(CharMatcher.is('.')).retainFrom("abc123.45xyz");
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Bring out the hospitality for specific character ranges without confusing hinges and brackets.

Danger ahead: Pitfalls and exceptions

replaceAll isn't a walk in the park. It has its demons:

• Input needs to be prim and proper. Messy inputs call for error handling.
• A slip in the regex pattern could throw a PatternSyntaxException. Arm yourself with try-catch blocks!