Java System.load() – Syntax & Examples

Java System.load() – Examples

In this tutorial, we will learn about the Java System.load() function, and learn how to use this function to load a native library into System, with the help of examples.

load(String filename)

System.load() loads the native library specified by the filename argument.

The filename must be an absolute path to the file you would like to load.

Syntax

The syntax of load() function is

load(String filename)

where

Parameter	Description
filename	Absolute path of the file to load.

Returns

The function returns void.

Example 1 – load(String filename)

In this example, we will load a .dll file. Absolute path of the file is given to load() method as argument.

Java Program

public class Example {
	public static void main(String args[]) {
		System.out.println("Loading dll..");  

		String filename = "C:\\Users\\TutorialKart\\.eclipse\\org.eclipse.platform_4.4.1_1845977472_win32_win32_x86_64\\configuration\\org.eclipse.osgi\\86\\0\\.cp\\os\\win32\\x86_64\\localfile_1_0_0.dll"; 
		System.load(filename);  

		System.out.println("Loading finished.");  
	}  
} 

Output

Loading dll..
Loading finished.

Example 2 – load(String filename) – File Path Incorrect

In this example, we will provide an incorrect path as filename to load() method. load() method should throw java.lang.UnsatisfiedLinkError.

Java Program

public class Example {
	public static void main(String args[]) {
		System.out.println("Loading dll..");  

		String filename = "C:\\nothing.dll"; 
		System.load(filename);  

		System.out.println("Loading finished.");  
	}  
} 

Output

Loading dll..
Exception in thread "main" java.lang.UnsatisfiedLinkError: Can't load library: C:\nothing.dll
	at java.base/java.lang.ClassLoader.loadLibrary(Unknown Source)
	at java.base/java.lang.Runtime.load0(Unknown Source)
	at java.base/java.lang.System.load(Unknown Source)
	at Example.main(Example.java:6)

Example 3 – load(filename) – Null filename

In this example, we will provide a null value as filename to load() method. load() method should throw java.lang.NullPointerException.

Java Program

public class Example {
	public static void main(String args[]) {
		System.out.println("Loading dll..");  

		String filename = null; 
		System.load(filename);  

		System.out.println("Loading finished.");  
	}  
} 

Output

Loading dll..
Exception in thread "main" java.lang.NullPointerException
	at java.base/java.io.File.<init>(Unknown Source)
	at java.base/java.lang.Runtime.load0(Unknown Source)
	at java.base/java.lang.System.load(Unknown Source)
	at Example.main(Example.java:6)

Conclusion

In this Java Tutorial, we have learnt the syntax of Java System.load() function, and also learnt how to use this function with the help of examples.