java double to string with comma

To convert a double value to a String with a comma as the decimal separator in Java, you can use the DecimalFormat class from the java.text package.

Here's an example of how to do this:

double d = 12345.678;

// Create a DecimalFormat object with a pattern that includes a comma as the decimal separator
DecimalFormat df = new DecimalFormat("#,##0.00");

// Use the format() method to convert the double to a String
String str = df.format(d);  // str is now "12,345.68"

This will convert the double value to a String with a comma as the decimal separator and two decimal places.

You can specify a different pattern in the DecimalFormat constructor to control the formatting of the double value. For example, you can use the # symbol to represent optional digits, the 0 symbol to represent required digits, and the , symbol to add a comma as a thousand separator.

It's important to note that the DecimalFormat class is not thread-safe and should be used with caution in multi-threaded environments. Alternatively, you can use the NumberFormat class from the java.text package or the String.format() method to convert a double to a String with a comma as the decimal separator.