In Java, there are several ways to convert a string to long. A long is a data type that can store a large whole number. Converting a string to long is useful when you need to do mathematical operations with the number or when you need to store the number in a long variable. In this article, we will discuss various methods to convert a string to long in Java.
Method 1: Parsing the String to Long using Long.parseLong()
The most commonly used method to convert a string to a long is using the parseLong() method in the Long class. This method takes a string as input and returns a long.
Example:
String number = "123456789";
long long_number = Long.parseLong(number);
System.out.println("Long number: " + long_number);
Output:
Long number: 123456789
The parseLong() method throws a NumberFormatException if the string cannot be parsed into a long. Therefore, it is important to handle this exception in your code.
Example:
String invalid_number = "hello";
try {
long long_number = Long.parseLong(invalid_number);
} catch (NumberFormatException e) {
System.err.println("Invalid number: " + invalid_number);
}
Output:
Invalid number: hello
Method 2: Using the valueOf() method of Long class
Another way to convert a string to long is using the valueOf() method of the Long class. This method returns a Long object, which can be converted to a long using the longValue() method.
Example:
String number = "123456789";
Long long_obj = Long.valueOf(number);
long long_number = long_obj.longValue();
System.out.println("Long number: " + long_number);
Output:
Long number: 123456789
Method 3: Using the BigInteger class
If the number is larger than the range of a long, you can use the BigInteger class to convert a string to a long. The BigInteger class can handle large whole numbers that exceed the range of a long.
Example:
String number = "123456789123456789";
BigInteger big_integer = new BigInteger(number);
long long_number = big_integer.longValue();
System.out.println("Long number: " + long_number);
Output:
Long number: 123456789123456789
Method 4: Using the Scanner class
The Scanner class can be used to convert a string to a long. This class provides convenience methods to read input data from the console and convert it to various data types.
Example:
String number = "123456789";
Scanner scanner = new Scanner(number);
long long_number = scanner.nextLong();
System.out.println("Long number: " + long_number);
Output:
Long number: 123456789
Conclusion
In this article, we discussed various methods to convert a string to long in Java. The Long.parseLong() method is the most commonly used method to convert a string to long. The valueOf() method of the Long class and the Scanner class can also be used to convert a string to long. If the number is larger than the range of a long, the BigInteger class can be used to handle large whole numbers. It is important to handle the NumberFormatException when using the parseLong() method to avoid runtime errors.
let's dive a bit deeper into the methods we discussed earlier.
Method 1: Parsing the String to Long using Long.parseLong()
The parseLong() method in the Long class is a very efficient method to convert a string to a long. It is a widely used method in Java for converting string to integer and long. The method does not require any extra memory and is very effective in handling small to medium-sized long values. However, if the number in the string is larger than the maximum value for a long, it will throw a NumberFormatException.
In order to avoid this, you can provide a try-catch block to handle the exception, and show a message to the user regarding the invalid number. It is always better to anticipate these exceptions and code accordingly.
Method 2: Using the valueOf() method of Long class
The valueOf() method of the Long class also converts a string to a long but is different from the parseLong() method. This method has a higher memory usage because it returns a Long object instead of primitive long value. Interestingly, it internally calls the parseLong() method to parse the string, but the difference is that parseLong() returns a primitive long value, while valueOf() returns a Long object.
This approach is useful when you have to store the result of the conversion in an object-oriented way. For example, if you want to pass the converted long value to another method that requires an object of Long class as input, you can use this approach.
Method 3: Using the BigInteger class
The BigInteger class is a powerful class that can hold values of any size and can handle mathematical operations with very large numbers. If the value of the number in the string exceeds the maximum value of a long, we can use this class for handling them.
The BigInteger class is a bit slower in execution due to the extra overhead that the OOP concept brings. It requires extra memory to allocate an object and creates some overhead in garbage collection. But this method is very effective in handling large numbers, and you can use it when you need to handle very large numbers.
Method 4: Using the Scanner class
The Scanner class is an efficient way to convert a string to a long value. It is a useful way when you are dealing with input from keyboard, files, or network streams. It is an effective way to scan strings and convert them to other data types in Java. The nextLong() method of the Scanner class reads the next long number from the input stream and converts it to a long data type.
This method is useful when you are dealing with a string that contains a single number, and there are no other characters in the string. Otherwise, you may end up with runtime errors due to wrong input format.
Conclusion
In conclusion, there are several methods to convert a string to a long in Java. Each method has its own advantages and disadvantages, and it is important to choose the right method based on your requirements. The Long.parseLong() method is the most commonly used method, and it is efficient for handling small to medium-sized numbers. The BigInteger class is useful when you are dealing with large numbers that exceed the range of a long. The valueOf() method of Long class is useful when you need to store the result of the conversion in an object-oriented way. The Scanner class is useful when you are dealing with input from keyboard or network streams.
Popular questions
- What is the most commonly used method to convert a string to long in Java?
- The most commonly used method is Long.parseLong().
- What happens if the string cannot be parsed into a long in the Long.parseLong() method?
- It throws a NumberFormatException.
- Which method creates a Long object instead of a primitive long value?
- The valueOf() method of the Long class.
- Which class can handle mathematical operations with very large numbers?
- The BigInteger class.
- When is the Scanner class method useful for converting a string to long?
- When you are dealing with input from keyboard or network streams and the string contains a single number, without other characters.
Tag
Conversion
