Regular expression to match escaped characters (quotes)

The problem with all the other answers is they only match for the initial obvious testing, but fall short to further scrutiny. For example, all of the answers expect that the very first quote will not be escaped. But most importantly, escaping is a more complex process than just a single backslash, because that backslash itself can be escaped. Imagine trying to actually match a string which ends with a backslash. How would that be possible?

This would be the pattern you are looking for. It doesn't assume that the first quote is the working one, and it will allow for backslashes to be escaped.

(?<!\\)(?:\\{2})*"(?:(?<!\\)(?:\\{2})*\\"|[^"])+(?<!\\)(?:\\{2})*"

Try this one... It prefers the \", if that matches, it will pick it, otherwise it will pick ".

"((?:\\"|[^"])*)"

Once you have matched the string, you'll need to take the first captured group's value and replace \" with ".

Edit: Fixed grouping logic.

Please find in the below code comprising expression evaluation for String, Number and Decimal.

public static void commaSeparatedStrings() {        
    String value = "'It\\'s my world', 'Hello World', 'What\\'s up', 'It\\'s just what I expected.'";

    if (value.matches("'([^\'\\\\]*(?:\\\\.[^\'\\\\])*)[\\w\\s,\\.]+'(((,)|(,\\s))'([^\'\\\\]*(?:\\\\.[^\'\\\\])*)[\\w\\s,\\.]+')*")) {
        System.out.println("Valid...");
    } else {
        System.out.println("Invalid...");
    }
}

/**
 * 
 */
public static void commaSeparatedDecimals() {
    String value = "-111.00, 22111.00, -1.00";
    // "\\d+([,]|[,\\s]\\d+)*"
    if (value.matches(
            "^([-]?)\\d+\\.\\d{1,10}?(((,)|(,\\s))([-]?)\\d+\\.\\d{1,10}?)*")) {
        System.out.println("Valid...");
    } else {
        System.out.println("Invalid...");
    }
}

/**
 * 
 */
public static void commaSeparatedNumbers() {
    String value = "-11, 22, -31";      
    if (value.matches("^([-]?)\\d+(((,)|(,\\s))([-]?)\\d+)*")) {
        System.out.println("Valid...");
    } else {
        System.out.println("Invalid...");
    }
}

Here is one that I've used in the past:

("[^"\\]*(?:\\.[^"\\]*)*")

This will capture quoted strings, along with any escaped quote characters, and exclude anything that doesn't appear in enclosing quotes.

For example, the pattern will capture "This is valid" and "This is \" also \" valid" from this string:

"This is valid" this won't be captured "This is \" also \" valid"

This pattern will not match the string "I don't \"have\" a closing quote, and will allow for additional escape codes in the string (e.g., it will match "hello world!\n").

Of course, you'll have to escape the pattern to use it in your code, like so:

"(\"[^\"\\\\]*(?:\\\\.[^\"\\\\]*)*\")"