Java System.loadLibrary() – Syntax & Examples

Java System.loadLibrary() – Examples

In this tutorial, we will learn about the Java System.loadLibrary() function, and learn how to use this function with the help of examples.

loadLibrary(String libname)

System.loadLibrary(libname) loads the native library specified by the libname argument.

Make sure the library file is present in any of the path specified by java.library.path.

Syntax

The syntax of loadLibrary() function is

loadLibrary(String libname)

where

Parameter	Description
libname	The name of library.

Returns

The function returns void.

Example 1 – loadLibrary(libname)

In this example, we will load a dll present in the Java library path.

awt.dll is present in the location C:\Program Files\Java\jre-10.0.1\bin. And this location is part of java.library.path.

Java Program

public class Example {
	public static void main(String args[]) {
		System.out.println("Loading Library...");
		String libname = "awt";
		System.loadLibrary(libname);
		System.out.println("Library Loaded.");
	}  
}

Output

Loading Library...
Library Loaded.

Example 2 – loadLibrary() – With Extension

In this example, we will provide the extension as well for the library name to loadLibrary() method. loadLibrary() throws java.lang.UnsatisfiedLinkError. So, do not provide the extension in the library name.

Java Program

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

Output

Loading Library...
Exception in thread "main" java.lang.UnsatisfiedLinkError: no awt.dll in java.library.path: [C:\Program Files\Java\jre-10.0.1\bin, C:\WINDOWS\Sun\Java\bin, C:\WINDOWS\system32, ., .]
	at java.base/java.lang.ClassLoader.loadLibrary(Unknown Source)
	at java.base/java.lang.Runtime.loadLibrary0(Unknown Source)
	at java.base/java.lang.System.loadLibrary(Unknown Source)
	at Example.main(Example.java:5)

Example 3 – loadLibrary(libname) – Null libname

In this example, we will pass null as argument for library name to loadLibrary() method. loadLibrary() throws java.lang.NullPointerException. Make sure that the library name is not null.

Java Program

public class Example {
	public static void main(String args[]) {
		System.out.println("Loading Library...");
		String libname = null;
		System.loadLibrary(libname);
		System.out.println("Library Loaded.");
	}  
}

Output

Loading Library...
Exception in thread "main" java.lang.NullPointerException
	at java.base/java.lang.Runtime.loadLibrary0(Unknown Source)
	at java.base/java.lang.System.loadLibrary(Unknown Source)
	at Example.main(Example.java:5)

Example 4 – loadLibrary(libname) – Library not present

In this example, we will try to load a library which is not present anywhere in the Java library paths. In such cases, loadLibrary() throws java.lang.UnsatisfiedLinkError.

Java Program

public class Example {
	public static void main(String args[]) {
		System.out.println("Loading Library...");
		String libname = "nolib";
		System.loadLibrary(libname);
		System.out.println("Library Loaded.");
	}  
}

Output

Loading Library...
Exception in thread "main" java.lang.UnsatisfiedLinkError: no nolib in java.library.path: [C:\Program Files\Java\jre-10.0.1\bin, C:\WINDOWS\Sun\Java\bin, C:\WINDOWS\system32, ., .]
	at java.base/java.lang.ClassLoader.loadLibrary(Unknown Source)
	at java.base/java.lang.Runtime.loadLibrary0(Unknown Source)
	at java.base/java.lang.System.loadLibrary(Unknown Source)
	at Example.main(Example.java:5)

Conclusion

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