javachk

Error message based on Java feature support

Syntax

MSG = javachk(feature)

javachk(feature,component)

Description

MSG = javachk(feature) returns a generic error message if the specified Java^® feature is not available in the current MATLAB^® session.

javachk(feature,component) also names the specified component in the error message.

Examples

Generate Error If Java Not Available

To test if Java is available before calling a Java command, use these statements. The isempty function is true when there is no error.

if isempty(javachk('jvm'))
   scalar = java.lang.Double(5);
end

Test Java Availability in User-Defined Script

To provide context in the javachk error message, add the optional text parameter to the javachk function.

Create a script, myFile.m, with the following statements. The script checks if Java is available before calling Java to create a frame.

error(javachk('awt','myFile'))
myFrame = java.awt.Frame;
myFrame.setVisible(1)

Start MATLAB from the Linux^® system prompt.

matlab -nojvm

Run the script.

myFile

If Java is not available, then MATLAB displays this error, identifying the source as the myFile script.

Error using myFile (line 1)
myFile is not supported because:
Java is not currently available.

Input Arguments

feature — Java feature

'awt' | 'desktop' | 'jvm' | 'swing'

Java feature, specified as one of these values.

'awt'	UI components in the Java Abstract Window Toolkit (AWT) are available.
'desktop'	MATLAB interactive desktop is running.
'jvm'	Java Virtual Machine software (JVM™) is running.
'swing'	Swing components (Java lightweight UI components in the Java Foundation Classes) are available.

component — Identifier

string | character vector

Identifier, specified as a string or a character vector, to display in the error message.

Data Types: string | char

Output Arguments

MSG — Error message

structure

Error message, returned as a structure with the following fields. If the feature is available, javachk returns an error structure with empty fields.

message — Message

character vector | empty

Message, specified as a character vector.

identifier — Identifier

character vector | empty

Identifier, specified as a character vector.