Here is your answer:

    String regex = "(?<=[\\d])(,)(?=[\\d])";
    Pattern p = Pattern.compile(regex);
    String str = "Your input";
    Matcher m = p.matcher(str);
    str = m.replaceAll("");
    System.out.println(str);

This only affects NUMBERS, not strings, as you asked.

Try adding that in your main method. Or try this one, it receives input:

       String regex = "(?<=[\\d])(,)(?=[\\d])";
        Pattern p = Pattern.compile(regex);
        System.out.println("Value?: ");
            Scanner scanIn = new Scanner(System.in);
            String str = scanIn.next();
        Matcher m = p.matcher(str);
        str = m.replaceAll("");
        System.out.println(str);

Is this comma a decimal separator or are these two numbers? In the first case you must provide Locale to NumberFormat class that uses comma as decimal separator:

NumberFormat.getNumberInstance(Locale.FRANCE).parse("265,858")

This results in 265.858. But using US locale you'll get 265858:

NumberFormat.getNumberInstance(java.util.Locale.US).parse("265,858")

That's because in France they treat comma as decimal separator while in US - as grouping (thousand) separator.

If these are two numbers - String.split() them and parse two separate strings independently.

do like this

NumberFormat format = NumberFormat.getCurrencyInstance();
Number number = format.parse("\$123,456.78");
System.out.println(number.toString());

output

123456.78

In this cases I use a simple trick:

String SEPARATOR = "";
for(i = 0; i < n; i++) {
    data[i] = input.nextInt();
}
for(i = 0; i < n; i++) {
    if((i + 1) % 2 == 0) {
        System.out.print(SEPARATOR + data[i]);
        sum += data[i];
        SEPARATOR = ",";
    }
}

You have a DecimalFormat which you're using to format the value. Use the same object to parse the value, instead of using Double.valueOf.

Additionally:

• Try to avoid formatting/parsing cycles where possible. Keep the value as a number for almost your whole code base, only formatting for presentation and only parsing for user input
• Don't use double for currency values; use BigDecimal which will reduce the surprises you get when it comes to "inaccurate" arithmetic
• Follow Java naming conventions wherever possible. StrCash_price_deal is horrible in both casing and underscore-ness

If you just want to replace the comma, you do:

String newOne = oldString.replaceAll(",","");

If you want to get each id in a new integer (which sounds more what you want from the description), you can do:

String[] ids = oldString.split(",");

you can then loop over the array to get the individual ids:

for (String id : ids ) {
   doSomethingWithId(id);
}

You have to disable the grouping in your NumberFormat object like this:

NumberFormat format = NumberFormat.getIntegerInstance();
format.setGroupingUsed(false);
myNumberBox = new JFormattedTextField(format);

See: NumberFormat.setGroupingUsed

i think you are looking for setting the number format.. here is the documentation from Struts 2 regarding this.

format.number = {0} # i think this should do

 public static void main(String args[]) throws IOException

    {

        String regex = "(?<=[\\d])(,)(?=[\\d])";
        Pattern p = Pattern.compile(regex);
        String str = "John loves cakes and he always orders them by dialing \"989,444 1234\". Johns credentials are as follows\" \"Name\":\"John\", \"Jr\", \"Mobile\":\"945,234,1110\"";
        Matcher m = p.matcher(str);
        str = m.replaceAll("");
        System.out.println(str);
    }

Output

John loves cakes and he always orders them by dialing "989444 1234". Johns credentials are as follows" "Name":"John", "Jr", "Mobile":"9452341110"

Java float doesn't have that much precision, which you can see with

float f = 23000.2359f;
System.out.println(f);

which outputs

23000.236

To get the output you want, you could use a double like

double d = 23000.2359;
String v = String.valueOf(d).replace(".", "");
int val = Integer.parseInt(v);
System.out.println(val);

Output is (the requested)

230002359

You can modify the loop

for(int i = 0; i < numbers.length - 1; i++) {
  System.out.print(numbers[i] + ",");
}
System.out.print(numbers[numbers.length - 1]);

Or use streams

 Arrays.stream(numbers).collect(Collectors.joining(","));

There is a caveat that you need to be aware about since you're trying to use an intermediate int variable:

• The range of double values is far broader than the range of long (and int obviously). So by converting a double into a long and then again to double you might lose the data.

Here are some ways how it can be done without losing the data:

1. Modular division:

double num = 59.012;

double wholeNum2 = num - num % 1;

2. Static method Math.floor():

double num = 59.012;

double wholeNum = Math.floor(num);

3. DecimalFormat class, that allow to specify a string pattern and format a number accordingly:

double num = 59.012;

NumberFormat format = new DecimalFormat("0");
double wholeNum = Double.parseDouble(format.format(num)); // parsing the formatted string

All examples above will give you the output 59.0 is you print the variable wholeNum.

When you need to obtain a double value as a result with the fractional part dropped, options 1 and 2 are preferable. But a string representing this number will still contain a dot and one zero .0 at the end.

But if you need to get the result as a String containing only the integer part of a double number, then DecimalFormat (as well String.format() that was mentioned in the comments) will help you to get rid of the fractional part completely.

NumberFormat format = new DecimalFormat("0");

System.out.println(format.format(59.012));

Output:

59

You loose the precision when you go via .doubleValue().

You need to store it as a BigDecimal right away. I suggest you use DecimalFormat and setParseBigDecimal to true.

DecimalFormat nf = new DecimalFormat("###,###.###");
nf.setParseBigDecimal(true);
BigDecimal bd = ((BigDecimal) nf.parse("999,999,999,999,999.999"))
                        .setScale(3,BigDecimal.ROUND_HALF_UP);

System.out.println(bd);  // 999999999999999.999