The Long.getLong()
method in Java is used to retrieve the long value of a system property. This method can return a default value if the specified property does not exist or cannot be parsed as a long.
Table of Contents
- Introduction
getLong()
Method Syntax- Examples
- Retrieving an Existing System Property
- Retrieving a Non-Existing System Property with Default Value
- Handling Non-Long Property Values
- Real-World Use Case
- Conclusion
Introduction
The Long.getLong()
method is a static method in the Long
class in Java. It retrieves the long value of a system property. If the system property is not defined or cannot be parsed as a long, the method can return null
or a specified default value.
getLong()() Method Syntax
The Long.getLong()
method has three overloaded versions:
1. Retrieve a Long Property
public static Long getLong(String nm)
- nm: The name of the system property.
The method returns:
- The long value of the system property, or
null
if the property does not exist or cannot be parsed as a long.
2. Retrieve a Long Property with Default Value
public static Long getLong(String nm, long val)
- nm: The name of the system property.
- val: The default value to return if the property does not exist or cannot be parsed as a long.
The method returns:
- The long value of the system property, or the specified default value if the property does not exist or cannot be parsed as a long.
3. Retrieve a Long Property with Default Value (Long)
public static Long getLong(String nm, Long val)
- nm: The name of the system property.
- val: The default
Long
value to return if the property does not exist or cannot be parsed as a long.
The method returns:
- The long value of the system property, or the specified default
Long
value if the property does not exist or cannot be parsed as a long.
Examples
Retrieving an Existing System Property
You can retrieve an existing system property and parse it as a long.
Example
public class GetLongExample {
public static void main(String[] args) {
// Set a system property for demonstration
System.setProperty("example.property", "123456789");
// Retrieve the system property as a long
Long value = Long.getLong("example.property");
System.out.println("Long value of 'example.property': " + value);
}
}
Output:
Long value of 'example.property': 123456789
In this example, the system property example.property
is set to "123456789"
, and the method retrieves it as a long.
Retrieving a Non-Existing System Property with Default Value
You can retrieve a non-existing system property and provide a default value to return if the property does not exist.
Example
public class GetLongWithDefaultExample {
public static void main(String[] args) {
// Retrieve the system property as a long with a default value
Long value = Long.getLong("non.existing.property", 987654321L);
System.out.println("Long value of 'non.existing.property': " + value);
}
}
Output:
Long value of 'non.existing.property': 987654321
In this example, the system property non.existing.property
does not exist, so the method returns the default value 987654321L
.
Handling Non-Long Property Values
If the system property cannot be parsed as a long, the method returns null
or the specified default value.
Example
public class GetLongInvalidPropertyExample {
public static void main(String[] args) {
// Set a system property with a non-long value for demonstration
System.setProperty("invalid.property", "abc");
// Retrieve the system property as a long with a default value
Long value = Long.getLong("invalid.property", 12345L);
System.out.println("Long value of 'invalid.property': " + value);
}
}
Output:
Long value of 'invalid.property': 12345
In this example, the system property invalid.property
is set to "abc"
, which cannot be parsed as a long, so the method returns the default value 12345L
.
Real-World Use Case
Configuring Application Settings
In a real-world application, you might use the Long.getLong()
method to configure application settings based on system properties.
Example
public class AppConfigExample {
public static void main(String[] args) {
// Set system properties for demonstration
System.setProperty("app.maxConnections", "200");
System.setProperty("app.timeout", "5000");
// Retrieve the settings as long values with default values
Long maxConnections = Long.getLong("app.maxConnections", 100L);
Long timeout = Long.getLong("app.timeout", 3000L);
System.out.println("Max Connections: " + maxConnections);
System.out.println("Timeout: " + timeout);
}
}
Output:
Max Connections: 200
Timeout: 5000
In this example, the system properties app.maxConnections
and app.timeout
are set and retrieved as long values with default values.
Conclusion
The Long.getLong()
method in Java is a powerful and useful tool for retrieving long values from system properties. By understanding how to use this method, you can efficiently handle tasks that involve parsing and retrieving configuration values in your Java applications. Whether you are dealing with existing properties, providing default values, or handling non-long values, the getLong()
method provides a reliable solution for these tasks.