You can draw from an extensive collection of existing Java® classes
or create your own class definitions to use with MATLAB®. This
section explains how to go about finding the class definitions that
you need or how to create classes of your own design. Once you have
the classes you need, defined in either individual
packages, or Java Archive (JAR) files, you can make them available
in the MATLAB workspace. This section also describes how to specify
the native method libraries used by Java code.
Following are Java class sources that you can use in the MATLAB workspace:
Java built-in classes — general-purpose
class packages, such as
java.util, included in
the Java language. See your Java language documentation
for descriptions of these packages.
Third-party classes — packages of special-purpose Java classes.
User-defined classes — Java classes or subclasses of existing classes that you define using a Java language development environment.
To define new Java classes and subclasses of existing classes, use a Java Development Kit external to MATLAB. For information on supported versions of JDK™ software, see the Supported and Compatible Compilers website.
After you create class definitions in
use your Java compiler to produce
from them. The next step is to make the class definitions in those
available for you to use in MATLAB.
MATLAB loads Java class definitions from files that are on the Java class path. The class path is a series of file and folder specifications that MATLAB uses to locate third-party and user-defined class definitions. When loading a Java class, MATLAB searches files and folders in the order they occur on the class path. The search ends when MATLAB finds a file that contains the class definition.
MATLAB segments the Java class path into a static path and a dynamic path. MATLAB provides the dynamic path as a convenience for when you develop your own Java classes. After you develop and debug a Java class, add the class to the static path.
To view the two
path segments, use the
Use the static path if you want the class functionality to run the same way it does in Java. Also, the static path offers better class loading performance than the dynamic path.
To add files
to the static path, create a
Create an ASCII text file and name the file
Enter the name of a Java class folder or jar file, one per line. For example:
To simplify folder specifications in cross-platform
environments, use these macros:
Save the file in your preferences folder. To view the location of the preferences folder, type:
Alternatively, save the
in your MATLAB startup folder. Classes specified in this file
override classes specified in the
in the preferences folder.
MATLAB reads the static class path only at
startup. If you edit
javaclasspath.txt or change
.class files while MATLAB is running,
restart MATLAB to put those changes into effect.
If you do not want MATLAB to use the entries in the
javaclasspath.txt file, start MATLAB with
Note: Do not put Java classes on the static path if they have dependencies on classes on the dynamic path.
You can change class definitions on the dynamic path without restarting MATLAB. Therefore, it is useful to put a user-defined Java class definition on the dynamic path while you develop and debug the class.
MATLAB always searches the static path before the dynamic path.
To add a class to the dynamic path,
javaaddpath functions. To remove an entry,
These functions clear all existing variables and global variables
in the workspace.
The dynamic path offers greater flexibility in changing the path. However, Java classes on the dynamic path might load more slowly than classes on the static path. Also, classes on the dynamic path might not behave identical to classes on the static path. If your class does not behave as expected, use the static path.
After developing a Java class, put the class on the static path.
To make third-party and user-defined Java classes available to MATLAB, place them on either the static or dynamic Java class path.
To put classes on the static
path, edit the
You can use individual classes (classes that are not part of
a package) in MATLAB. To make them available, specify the full
path to the folder you want to use for the
For example, to make available your compiled Java classes
in the file
the following entry to the static or dynamic class path:
To put this folder on the static class path, edit the
described in Static
To put this folder on the dynamic class path, use the following command:
You can access classes in a package. To make a package available to MATLAB, specify the full path to the parent folder of the highest level folder of the package path. This folder is the first component in the package name.
For example, if your Java class package
its classes in folder
the following folder to your static or dynamic class path:
You can use the
jar (Java Archive) tool
to create a JAR file, containing multiple Java classes and packages
in a compressed ZIP format. For information on
JAR files, consult your Java development documentation.
To make the contents of a JAR file available for use in MATLAB, specify the full path, including full file name, for the JAR file. You also can put the JAR file on the MATLAB path.
The path requirement for JAR files is different from the requirement
For example, to make available the JAR file
add the following file specification to your static or dynamic class
javaObjectEDT function instead
of the Java
Class.forName method. For example,
replace the following statement:
Normally, MATLAB loads a Java class automatically
when your code first uses it, for example, when you call its constructor.
However, be aware of the following exception. When you use the
on methods defined by Java classes, the function only acts on
the classes currently loaded into the MATLAB workspace.
which always operates on MATLAB classes,
whether they are loaded.
At any time during a MATLAB session, you can obtain a listing
of all the Java classes that are currently loaded. To do so,
inmem function as follows:
[M,X,J] = inmem
This function returns the list of Java classes in the output
J. (It also returns the names of all currently
loaded MATLAB functions in
M, and the names
of all currently loaded MEX-files in
Here is a sample of output from the
[m,x,j] = inmem; j
j = 'java.util.Date' 'com.mathworks.ide.desktop.MLDesktop'
Your MATLAB commands can refer to any Java class by its fully qualified name, which includes its package name. For example, the following are fully qualified names:
A fully qualified name can be long, making commands and functions, such as constructors, cumbersome to edit and to read. To refer to classes by the class name alone (without a package name), first import the fully qualified name into MATLAB.
MATLAB adds all classes that you import to a list called
the import list. You can see what classes are
on that list by typing
import, without any arguments.
Your code can refer to any class on the list by class name alone.
When called from a function,
the specified classes to the import list in effect for that function.
When invoked at the command prompt,
the base import list for your MATLAB platform.
For example, suppose that a function contains the following statements:
import java.lang.String import java.util.* java.awt.* import java.util.Enumeration
Any code that follows these
can refer to the
Enumeration classes without using the package
names. For example:
str = String('hello'); % Create java.lang.String object frm = Frame; % Create java.awt.Frame object methods Enumeration % List java.util.Enumeration methods
To remove the list of imported Java classes, type:
Java classes can dynamically load native methods using
the Java method
In order for the JVM™ software to locate the specified library
file, the folder containing it must be on the Java Library Path.
This path is established when the MATLAB runs the JVM software
You can augment the search path for native method libraries
by creating an ASCII text file named
your preferences folder. Follow these guidelines when editing this
Specify each new folder on a line by itself.
Specify only the folder names, not the names of the
DLL files. The
loadLibrary call reads the file
To simplify the specification of directories in cross-platform
environments, use any of these macros:
You also can create a
in your MATLAB startup folder. Libraries specified in this file
override libraries specified in the
in the preferences folder.
To disable using the
execute MATLAB with the
You can access Java classes that are contained in a JAR file once you have added the JAR file to either the static or dynamic class path. See Java Class Path for more information on how MATLAB uses the Java class path.
For example, suppose that you have a file,
in a folder called
work in your MATLAB root
folder. You can construct the path to this file using the
Add the JAR file to your dynamic class path using the
javaaddpath function (
the platform-correct folder separators):
You can now call the public methods in the JAR file. For information about these methods, refer to the JAR file documentation.