How to convert String to long in Java?

I got a simple question in Java: How can I convert a String that was obtained by Long.toString() to long?

Use Long.parseLong()

 Long.parseLong("0", 10)        // returns 0L
 Long.parseLong("473", 10)      // returns 473L
 Long.parseLong("-0", 10)       // returns 0L
 Long.parseLong("-FF", 16)      // returns -255L
 Long.parseLong("1100110", 2)   // returns 102L
 Long.parseLong("99", 8)        // throws a NumberFormatException
 Long.parseLong("Hazelnut", 10) // throws a NumberFormatException
 Long.parseLong("Hazelnut", 36) // returns 1356099454469L
 Long.parseLong("999")          // returns 999L

To convert a String to a Long (object), use Long.valueOf(String s).longValue();

See link

public class StringToLong {

   public static void main (String[] args) {

      // String s = "fred";    // do this if you want an exception

      String s = "100";

      try {
         long l = Long.parseLong(s);
         System.out.println("long l = " + l);
      } catch (NumberFormatException nfe) {
         System.out.println("NumberFormatException: " + nfe.getMessage());
      }

   }
}

Long.valueOf(String s) - obviously due care must be taken to protect against non-numbers if that is possible in your code.

There are a few ways to convert String to long:

1)

long l = Long.parseLong("200"); 

String numberAsString = "1234";
long number = Long.valueOf(numberAsString).longValue();

String numberAsString = "1234";
Long longObject = new Long(numberAsString);
long number = longObject.longValue();

We can shorten to:

String numberAsString = "1234";
long number = new Long(numberAsString).longValue();

Or just

long number = new Long("1234").longValue();

4. Using Decimal format:

String numberAsString = "1234";
DecimalFormat decimalFormat = new DecimalFormat("#");
try {
    long number = decimalFormat.parse(numberAsString).longValue();
    System.out.println("The number is: " + number);
} catch (ParseException e) {
    System.out.println(numberAsString + " is not a valid number.");
}