Java String to long

In Java, you can convert a String to a long using the parseLong() method of the Long class. This method parses the string and returns a long value.

1. Long.parseLong()

The Long.parseLong() method is the most common and straightforward way to convert a String to a long. If the String cannot be parsed as a valid long, it throws a NumberFormatException.

Example:

public class StringToLongExample {
    public static void main(String[] args) {
        String str = "1234567898765";
        
        // Convert String to long using parseLong()
        long num = Long.parseLong(str);
        
        System.out.println("Converted long: " + num);
    }
}

Output: Converted long: 1234567898765

Explanation:

1. Long.parseLong(str) converts the string str to a long.

2. If the string is not a valid representation of a long (e.g., contains non-numeric characters), it will throw a NumberFormatException.

2. Using Long.valueOf()

Another way to convert a String to a long is by using Long.valueOf(). This method returns a Long object (not a primitive long), and you can then convert it to a long if needed.

Example:

public class StringToLongExample {
    public static void main(String[] args) {
        String str = "765987654321";
        
        // Convert String to Long object using valueOf()
        Long longObj = Long.valueOf(str);
        
        // Convert Long object to primitive long
        long num = longObj.longValue();
        
        System.out.println("Converted long: " + num);
    }
}

Output: Converted long: 765987654321

Explanation:

1. Long.valueOf(str) returns a Long object, which you can convert to a primitive long using longValue().

2. If the string is not a valid number, it will throw a NumberFormatException.

How to handle Exceptions?

Both Long.parseLong() and Long.valueOf() throw a NumberFormatException if the string cannot be converted to a valid long. You should handle this exception to avoid program crashes.

public class StringToLongExample {
    public static void main(String[] args) {
        String str = "abcdef";  // Invalid number string
        
        try {
            long num = Long.parseLong(str);  // This will throw NumberFormatException
            System.out.println("Converted long: " + num);
        } catch (NumberFormatException e) {
            System.out.println("Error: Invalid number format");
        }
    }
}

Output: Error: Invalid number format