In this tutorial, you will learn how to convert String to long in Java. We can use Long wrapper class for this purpose, this class contains couple of methods that we can use for this conversion. There are following three ways to convert a String to a long value.
- Long.parseLong() Method
- Long.valueOf() Method
- Long(String s) Constructor of Long class
Java String to long Conversion Examples
1. Example Using Long.parseLong() Method
Long.parseLong(String): All the characters in the String must be digits except the first character, which can be a digit or a minus ‘-‘. For example: long var = Long.parseInt("-123"); is allowed and the value of var after conversion would be -123.
In this example, the string str2 has minus sign ‘-‘ in the beginning, which is why the value of variable num2 is negative in the output.
public class JavaExample {
public static void main(String[] args) {
String str = "21111";
String str2 = "-11111";
try {
//Conversion using parseLong(String) method
long num = Long.parseLong(str); //21111
long num2 = Long.parseLong(str2); //-11111
System.out.println(num+num2); //21111-11111 = 10000
} catch (NumberFormatException e) {
System.out.println("The string is not a valid long number.");
}
}
}
Output:
10000
2. Example Using Long.valueOf() Method
Long.valueOf(String): Converts the String to a long value. Similar to parseLong(String) method, this method also allows minus ‘-‘ as a first character in the String.
public class JavaExample {
public static void main(String[] args) {
String str = "11111";
String str2 = "88888";
try {
//Conversion using valueOf(String) method
long num = Long.valueOf(str);
long num2 = Long.valueOf(str2);
System.out.println(num);
System.out.println(num2);
} catch (NumberFormatException e) {
System.out.println("The string is not a valid long number.");
}
}
}
Output:
11111 88888
Important Points
- Handling NullFormatException: Both methods
valueOf()andparseLong()throw aNumberFormatExceptionif the string cannot be parsed as a validlong. It’s good practice to handle this exception while doing the conversion using these methods. - String Format: The String that we want to convert should be in the valid range of
longdata type in Java(-2^63 to 2^63-1).
3. Example Handling Invalid Input
In this example, we are demonstrating how to handle both valid and invalid string inputs during string to long conversion.
public class JavaExample {
public static void main(String[] args) {
String validStr = "12345";
String invalidStr = "12345xyz";
System.out.println("Valid String to long Conversion:");
convertStringToLong(validStr);
System.out.println("\nInvalid String to long Conversion:");
convertStringToLong(invalidStr);
}
public static void convertStringToLong(String str) {
try {
long number = Long.parseLong(str);
System.out.println("The long value is: " + number);
} catch (NumberFormatException e) {
System.out.println("Error: '" + str + "' is not a valid long number.");
}
}
}
Output:
Valid String Conversion:
The long value is: 12345
Invalid String Conversion:
Error: '12345abc' is not a valid long number.
4. Using the Constructor of Long class
Long(String s) constructor: Long class has a constructor that allows String argument and creates a new Long object representing the specified string in the equivalent long value. The string is converted to a long value in exactly the manner used by the parseLong(String) method for radix 10.
public class JavaExample {
public static void main(String[] args)
{
String str = "10000";
String str2 = "22222";
//Conversion using Long(String s) constructor
long num = new Long(str);
long num2 = new Long(str2);
System.out.println(num);
System.out.println(num2);
}
}
Output:
10000 22222
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