In java how to get substring from a string till a character c?

java

substring

string-manipulation

java-8

byAnton Shumikhin·Sep 12, 2024

You can extract a substring before a character c in Java using:

String input = "example string; with a character";
char c = ';';
String result = (input.indexOf(c) > -1) ? input.substring(0, input.indexOf(c)) : input;

Here, indexOf(c) locates the position of c, and substring(0, indexOf(c)) slices the string up to c. If c isn't present, the code returns the entire input.

Practical concerns, alternatives, and edge cases

Diving into the world of string manipulation can occasionally feel like opening Pandora's box. Let's tackle some potential issues:

Confirm 'c' exists...

If c is absent (i.e., indexOf(c) returns -1), you might want to alert the user, log the incident, or return the input — the choice is yours.

...But what if 'c' isn't alone?

If c occurs multiple times, indexOf(c) will give you the first occurrence, while lastIndexOf(c) reserves that last dance just for you.

Regex: for when patterns aren't as simple as 'c'

Regular expressions, or regex if you want to sound cool, can tackle complex patterns. To extract the substring before the first ".", you can do:

String result = input.split("\\.", 2)[0];

For the performance and memory-conscious folks

If you're engaged in a loop-based endeavour with string manipulation, StringBuilder is your best friend. StringBuilder - the Usain Bolt of string concat.

Consider importing reinforcements

External libraries, namely Apache Commons Lang, can make your life easier. Their method StringUtils.substringBefore(input, ".") might just be what you're looking for.

Whitespace and case sensitivity

Those sneaky extra spaces can often fly under the radar. Here's how to get rid of them:

String result = input.substring(0, input.indexOf(c)).trim();

Remember, case matters. a ≠ A. Use toLowerCase() or toUpperCase() to set up a common ground before your search.

explain-codes / Java / In java how to get substring from a string till a character c?

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