1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- Created by GNU Texinfo 6.8, https://www.gnu.org/software/texinfo/ -->
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Java Interface Functions (GNU Octave (version 7.3.0))</title>
<meta name="description" content="Java Interface Functions (GNU Octave (version 7.3.0))">
<meta name="keywords" content="Java Interface Functions (GNU Octave (version 7.3.0))">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<meta name="viewport" content="width=device-width,initial-scale=1">
<link href="index.html" rel="start" title="Top">
<link href="Concept-Index.html" rel="index" title="Concept Index">
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
<link href="Java-Interface.html" rel="up" title="Java Interface">
<link href="Set-up-the-JVM.html" rel="prev" title="Set up the JVM">
<style type="text/css">
<!--
a.copiable-anchor {visibility: hidden; text-decoration: none; line-height: 0em}
a.summary-letter {text-decoration: none}
blockquote.indentedblock {margin-right: 0em}
div.display {margin-left: 3.2em}
div.example {margin-left: 3.2em}
kbd {font-style: oblique}
pre.display {font-family: inherit}
pre.format {font-family: inherit}
pre.menu-comment {font-family: serif}
pre.menu-preformatted {font-family: serif}
span.nolinebreak {white-space: nowrap}
span.roman {font-family: initial; font-weight: normal}
span.sansserif {font-family: sans-serif; font-weight: normal}
span:hover a.copiable-anchor {visibility: visible}
ul.no-bullet {list-style: none}
-->
</style>
<link rel="stylesheet" type="text/css" href="octave.css">
</head>
<body lang="en">
<div class="subsection" id="Java-Interface-Functions">
<div class="header">
<p>
Previous: <a href="Set-up-the-JVM.html" accesskey="p" rel="prev">Set up the JVM</a>, Up: <a href="Java-Interface.html" accesskey="u" rel="up">Java Interface</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<span id="Java-Interface-Functions-1"></span><h4 class="subsection">A.4.4 Java Interface Functions</h4>
<p>The following functions are the core of the Java Interface. They provide a way
to create a Java object, get and set its data fields, and call Java methods
which return results to Octave.
</p>
<span id="index-object_002c-creating-a-Java-object"></span>
<span id="index-instance_002c-creating-a-Java-instance"></span>
<span id="XREFjavaObject"></span><dl class="def">
<dt id="index-javaObject"><span class="category">: </span><span><em><var>jobj</var> =</em> <strong>javaObject</strong> <em>(<var>classname</var>)</em><a href='#index-javaObject' class='copiable-anchor'> ¶</a></span></dt>
<dt id="index-javaObject-1"><span class="category">: </span><span><em><var>jobj</var> =</em> <strong>javaObject</strong> <em>(<var>classname</var>, <var>arg1</var>, …)</em><a href='#index-javaObject-1' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>Create a Java object of class <var>classsname</var>, by calling the class
constructor with the arguments <var>arg1</var>, …
</p>
<p>The first example below creates an uninitialized object, while the second
example supplies an initial argument to the constructor.
</p>
<div class="example">
<pre class="example">x = javaObject ("java.lang.StringBuffer")
x = javaObject ("java.lang.StringBuffer", "Initial string")
</pre></div>
<p><strong>See also:</strong> <a href="#XREFjavaMethod">javaMethod</a>, <a href="#XREFjavaArray">javaArray</a>.
</p></dd></dl>
<span id="index-array_002c-creating-a-Java-array"></span>
<span id="XREFjavaArray"></span><dl class="def">
<dt id="index-javaArray"><span class="category">: </span><span><em><var>jary</var> =</em> <strong>javaArray</strong> <em>(<var>classname</var>, <var>sz</var>)</em><a href='#index-javaArray' class='copiable-anchor'> ¶</a></span></dt>
<dt id="index-javaArray-1"><span class="category">: </span><span><em><var>jary</var> =</em> <strong>javaArray</strong> <em>(<var>classname</var>, <var>m</var>, <var>n</var>, …)</em><a href='#index-javaArray-1' class='copiable-anchor'> ¶</a></span></dt>
<dd>
<p>Create a Java array of size <var>sz</var> with elements of class <var>classname</var>.
</p>
<p><var>classname</var> may be a Java object representing a class or a string
containing the fully qualified class name. The size of the object may
also be specified with individual integer arguments <var>m</var>, <var>n</var>, etc.
</p>
<p>The generated array is uninitialized. All elements are set to null if
<var>classname</var> is a reference type, or to a default value (usually 0) if
<var>classname</var> is a primitive type.
</p>
<p>Sample code:
</p>
<div class="example">
<pre class="example">jary = javaArray ("java.lang.String", 2, 2);
jary(1,1) = "Hello";
</pre></div>
<p><strong>See also:</strong> <a href="#XREFjavaObject">javaObject</a>.
</p></dd></dl>
<p>There are many different variable types in Octave, but only ones created
through <code>javaObject</code> can use Java functions. Before using Java with an
unknown object the type can be checked with <code>isjava</code>.
</p>
<span id="XREFisjava"></span><dl class="def">
<dt id="index-isjava"><span class="category">: </span><span><em></em> <strong>isjava</strong> <em>(<var>x</var>)</em><a href='#index-isjava' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>Return true if <var>x</var> is a Java object.
</p>
<p><strong>See also:</strong> <a href="Built_002din-Data-Types.html#XREFclass">class</a>, <a href="Data-Types.html#XREFtypeinfo">typeinfo</a>, <a href="Built_002din-Data-Types.html#XREFisa">isa</a>, <a href="#XREFjavaObject">javaObject</a>.
</p></dd></dl>
<p>Once an object has been created it is natural to find out what fields the
object has, and to read (get) and write (set) them.
</p>
<span id="index-fields_002c-displaying-available-fields-of-a-Java-object"></span>
<p>In Octave the <code>fieldnames</code> function for structures has been overloaded
to return the fields of a Java object. For example:
</p>
<div class="example">
<pre class="example">dobj = javaObject ("java.lang.Double", pi);
fieldnames (dobj)
⇒
{
[1,1] = public static final double java.lang.Double.POSITIVE_INFINITY
[1,2] = public static final double java.lang.Double.NEGATIVE_INFINITY
[1,3] = public static final double java.lang.Double.NaN
[1,4] = public static final double java.lang.Double.MAX_VALUE
[1,5] = public static final double java.lang.Double.MIN_NORMAL
[1,6] = public static final double java.lang.Double.MIN_VALUE
[1,7] = public static final int java.lang.Double.MAX_EXPONENT
[1,8] = public static final int java.lang.Double.MIN_EXPONENT
[1,9] = public static final int java.lang.Double.SIZE
[1,10] = public static final java.lang.Class java.lang.Double.TYPE
}
</pre></div>
<span id="index-field_002c-returning-value-of-Java-object-field"></span>
<p>The analogy of objects with structures is carried over into reading and writing
object fields. To read a field the object is indexed with the ‘<samp>.</samp>’
operator from structures. This is the preferred method for reading fields, but
Octave also provides a function interface to read fields with <code>java_get</code>.
An example of both styles is shown below.
</p>
<div class="example">
<pre class="example">dobj = javaObject ("java.lang.Double", pi);
dobj.MAX_VALUE
⇒ 1.7977e+308
java_get ("java.lang.Float", "MAX_VALUE")
⇒ 3.4028e+38
</pre></div>
<span id="XREFjava_005fget"></span><dl class="def">
<dt id="index-java_005fget"><span class="category">: </span><span><em><var>val</var> =</em> <strong>java_get</strong> <em>(<var>obj</var>, <var>name</var>)</em><a href='#index-java_005fget' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>Get the value of the field <var>name</var> of the Java object <var>obj</var>.
</p>
<p>For static fields, <var>obj</var> can be a string representing the fully
qualified name of the corresponding class.
</p>
<p>When <var>obj</var> is a regular Java object, structure-like indexing can be
used as a shortcut syntax. For instance, the following two statements are
equivalent
</p>
<div class="example">
<pre class="example"> java_get (x, "field1")
x.field1
</pre></div>
<p><strong>See also:</strong> <a href="#XREFjava_005fset">java_set</a>, <a href="#XREFjavaMethod">javaMethod</a>, <a href="#XREFjavaObject">javaObject</a>.
</p></dd></dl>
<span id="index-field_002c-setting-value-of-Java-object-field"></span>
<span id="XREFjava_005fset"></span><dl class="def">
<dt id="index-java_005fset"><span class="category">: </span><span><em><var>obj</var> =</em> <strong>java_set</strong> <em>(<var>obj</var>, <var>name</var>, <var>val</var>)</em><a href='#index-java_005fset' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>Set the value of the field <var>name</var> of the Java object <var>obj</var> to
<var>val</var>.
</p>
<p>For static fields, <var>obj</var> can be a string representing the fully
qualified named of the corresponding Java class.
</p>
<p>When <var>obj</var> is a regular Java object, structure-like indexing can be
used as a shortcut syntax. For instance, the following two statements are
equivalent
</p>
<div class="example">
<pre class="example"> java_set (x, "field1", val)
x.field1 = val
</pre></div>
<p><strong>See also:</strong> <a href="#XREFjava_005fget">java_get</a>, <a href="#XREFjavaMethod">javaMethod</a>, <a href="#XREFjavaObject">javaObject</a>.
</p></dd></dl>
<span id="index-methods_002c-displaying-available-methods-of-a-Java-object"></span>
<p>To see what functions can be called with an object use <code>methods</code>. For
example, using the previously created <var>dobj</var>:
</p>
<div class="example">
<pre class="example">methods (dobj)
⇒
Methods for class java.lang.Double:
boolean equals(java.lang.Object)
java.lang.String toString(double)
java.lang.String toString()
…
</pre></div>
<p>To call a method of an object the same structure indexing operator ‘<samp>.</samp>’ is
used. Octave also provides a functional interface to calling the methods of an
object through <code>javaMethod</code>. An example showing both styles is shown
below.
</p>
<div class="example">
<pre class="example">dobj = javaObject ("java.lang.Double", pi);
dobj.equals (3)
⇒ 0
javaMethod ("equals", dobj, pi)
⇒ 1
</pre></div>
<span id="index-method_002c-invoking-a-method-of-a-Java-object"></span>
<span id="XREFjavaMethod"></span><dl class="def">
<dt id="index-javaMethod"><span class="category">: </span><span><em><var>ret</var> =</em> <strong>javaMethod</strong> <em>(<var>methodname</var>, <var>obj</var>)</em><a href='#index-javaMethod' class='copiable-anchor'> ¶</a></span></dt>
<dt id="index-javaMethod-1"><span class="category">: </span><span><em><var>ret</var> =</em> <strong>javaMethod</strong> <em>(<var>methodname</var>, <var>obj</var>, <var>arg1</var>, …)</em><a href='#index-javaMethod-1' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>Invoke the method <var>methodname</var> on the Java object <var>obj</var> with the
arguments <var>arg1</var>, ….
</p>
<p>For static methods, <var>obj</var> can be a string representing the fully
qualified name of the corresponding class.
</p>
<p>When <var>obj</var> is a regular Java object, structure-like indexing can be
used as a shortcut syntax. For instance, the two following statements are
equivalent
</p>
<div class="example">
<pre class="example"> ret = javaMethod ("method1", x, 1.0, "a string")
ret = x.method1 (1.0, "a string")
</pre></div>
<p><code>javaMethod</code> returns the result of the method invocation.
</p>
<p><strong>See also:</strong> <a href="Creating-a-Class.html#XREFmethods">methods</a>, <a href="#XREFjavaObject">javaObject</a>.
</p></dd></dl>
<p>The following three functions are used to display and modify the class path
used by the Java Virtual Machine. This is entirely separate from Octave’s
<code>PATH</code> variable and is used by the JVM to find the correct code to execute.
</p>
<span id="index-classpath_002c-displaying"></span>
<span id="index-classpath_002c-dynamic"></span>
<span id="index-dynamic-classpath-1"></span>
<span id="index-classpath_002c-static"></span>
<span id="index-static-classpath-1"></span>
<span id="XREFjavaclasspath"></span><dl class="def">
<dt id="index-javaclasspath"><span class="category">: </span><span><em></em> <strong>javaclasspath</strong> <em>()</em><a href='#index-javaclasspath' class='copiable-anchor'> ¶</a></span></dt>
<dt id="index-javaclasspath-1"><span class="category">: </span><span><em><var>dpath</var> =</em> <strong>javaclasspath</strong> <em>()</em><a href='#index-javaclasspath-1' class='copiable-anchor'> ¶</a></span></dt>
<dt id="index-javaclasspath-2"><span class="category">: </span><span><em>[<var>dpath</var>, <var>spath</var>] =</em> <strong>javaclasspath</strong> <em>()</em><a href='#index-javaclasspath-2' class='copiable-anchor'> ¶</a></span></dt>
<dt id="index-javaclasspath-3"><span class="category">: </span><span><em><var>clspath</var> =</em> <strong>javaclasspath</strong> <em>(<var>what</var>)</em><a href='#index-javaclasspath-3' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>Return the class path of the Java virtual machine in the form of a cell
array of strings.
</p>
<p>If called with no inputs:
</p>
<ul>
<li> If no output is requested, the dynamic and static classpaths are
printed to the standard output.
</li><li> If one output value <var>dpath</var> is requested, the result is the
dynamic classpath.
</li><li> If two output values<var>dpath</var> and <var>spath</var> are requested, the
first variable will contain the dynamic classpath and the second will
contain the static classpath.
</li></ul>
<p>If called with a single input parameter <var>what</var>:
</p>
<dl compact="compact">
<dt><span><code>"-dynamic"</code></span></dt>
<dd><p>Return the dynamic classpath.
</p>
</dd>
<dt><span><code>"-static"</code></span></dt>
<dd><p>Return the static classpath.
</p>
</dd>
<dt><span><code>"-all"</code></span></dt>
<dd><p>Return both the static and dynamic classpath in a single cellstr.
</p></dd>
</dl>
<p><strong>See also:</strong> <a href="#XREFjavaaddpath">javaaddpath</a>, <a href="#XREFjavarmpath">javarmpath</a>.
</p></dd></dl>
<span id="index-javaaddpath"></span>
<span id="index-classpath_002c-adding-new-path"></span>
<span id="index-path_002c-adding-to-classpath"></span>
<span id="index-classpath_002c-dynamic-1"></span>
<span id="index-dynamic-classpath_002c-adding-new-path"></span>
<span id="XREFjavaaddpath"></span><dl class="def">
<dt id="index-javaaddpath-1"><span class="category">: </span><span><em></em> <strong>javaaddpath</strong> <em>(<var>clspath</var>)</em><a href='#index-javaaddpath-1' class='copiable-anchor'> ¶</a></span></dt>
<dt id="index-javaaddpath-2"><span class="category">: </span><span><em></em> <strong>javaaddpath</strong> <em>(<var>clspath1</var>, …)</em><a href='#index-javaaddpath-2' class='copiable-anchor'> ¶</a></span></dt>
<dt id="index-javaaddpath-3"><span class="category">: </span><span><em></em> <strong>javaaddpath</strong> <em>({<var>clspath1</var>, …})</em><a href='#index-javaaddpath-3' class='copiable-anchor'> ¶</a></span></dt>
<dt id="index-javaaddpath-4"><span class="category">: </span><span><em></em> <strong>javaaddpath</strong> <em>(…, "-end")</em><a href='#index-javaaddpath-4' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>Add <var>clspath</var> to the beginning of the dynamic class path of the
Java virtual machine.
</p>
<p><var>clspath</var> may either be a directory where <samp>.class</samp> files are
found, or a <samp>.jar</samp> file containing Java classes. Multiple paths may
be added at once by specifying additional arguments, or by using a cell
array of strings.
</p>
<p>If the final argument is <code>"-end"</code>, append the new element to the
end of the current classpath.
</p>
<p><strong>See also:</strong> <a href="#XREFjavarmpath">javarmpath</a>, <a href="#XREFjavaclasspath">javaclasspath</a>.
</p></dd></dl>
<span id="index-classpath_002c-removing-path"></span>
<span id="index-path_002c-removing-from-classpath"></span>
<span id="XREFjavarmpath"></span><dl class="def">
<dt id="index-javarmpath"><span class="category">: </span><span><em></em> <strong>javarmpath</strong> <em>(<var>clspath</var>)</em><a href='#index-javarmpath' class='copiable-anchor'> ¶</a></span></dt>
<dt id="index-javarmpath-1"><span class="category">: </span><span><em></em> <strong>javarmpath</strong> <em>(<var>clspath1</var>, …)</em><a href='#index-javarmpath-1' class='copiable-anchor'> ¶</a></span></dt>
<dt id="index-javarmpath-2"><span class="category">: </span><span><em></em> <strong>javarmpath</strong> <em>({<var>clspath1</var>, …})</em><a href='#index-javarmpath-2' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>Remove <var>clspath</var> from the dynamic class path of the Java virtual
machine.
</p>
<p><var>clspath</var> may either be a directory where <samp>.class</samp> files are found,
or a <samp>.jar</samp> file containing Java classes. Multiple paths may be
removed at once by specifying additional arguments, or by using a cell array
of strings.
</p>
<p><strong>See also:</strong> <a href="#XREFjavaaddpath">javaaddpath</a>, <a href="#XREFjavaclasspath">javaclasspath</a>.
</p></dd></dl>
<p>The following functions provide information and control over the interface
between Octave and the Java Virtual Machine.
</p>
<span id="XREFjavachk"></span><dl class="def">
<dt id="index-javachk"><span class="category">: </span><span><em></em> <strong>javachk</strong> <em>(<var>feature</var>)</em><a href='#index-javachk' class='copiable-anchor'> ¶</a></span></dt>
<dt id="index-javachk-1"><span class="category">: </span><span><em></em> <strong>javachk</strong> <em>(<var>feature</var>, <var>caller</var>)</em><a href='#index-javachk-1' class='copiable-anchor'> ¶</a></span></dt>
<dt id="index-javachk-2"><span class="category">: </span><span><em><var>msg</var> =</em> <strong>javachk</strong> <em>(…)</em><a href='#index-javachk-2' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>Check for the presence of the Java <var>feature</var> in the current session.
Return an error structure if <var>feature</var> is not available, not enabled,
or not recognized.
</p>
<p>Possible recognized features are:
</p>
<dl compact="compact">
<dt><span><code>"awt"</code></span></dt>
<dd><p>Abstract Window Toolkit for GUIs.
</p>
</dd>
<dt><span><code>"desktop"</code></span></dt>
<dd><p>Interactive desktop is running.
</p>
</dd>
<dt><span><code>"jvm"</code></span></dt>
<dd><p>Java Virtual Machine.
</p>
</dd>
<dt><span><code>"swing"</code></span></dt>
<dd><p>Swing components for lightweight GUIs.
</p></dd>
</dl>
<p>If <var>feature</var> is not supported, a scalar struct with field
<code>"message"</code> and <code>"identifier"</code> is returned. The field
<code>"message"</code> contains an error message mentioning <var>feature</var> as
well as the optional user-specified <var>caller</var>. This structure is
suitable for passing in to the <code>error</code> function.
</p>
<p>If <var>feature</var> is supported and available, an empty struct array is
returned with fields <code>"message"</code> and <code>"identifier"</code>.
</p>
<p><code>javachk</code> determines if specific Java features are available in an
Octave session. This function is provided for scripts which may alter
their behavior based on the availability of Java or specific Java runtime
features.
</p>
<p>Compatibility Note: The feature <code>"desktop"</code> is never available since
Octave has no Java-based desktop.
</p>
<p><strong>See also:</strong> <a href="#XREFusejava">usejava</a>, <a href="Raising-Errors.html#XREFerror">error</a>.
</p></dd></dl>
<span id="XREFusejava"></span><dl class="def">
<dt id="index-usejava"><span class="category">: </span><span><em></em> <strong>usejava</strong> <em>(<var>feature</var>)</em><a href='#index-usejava' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>Return true if the Java element <var>feature</var> is available.
</p>
<p>Possible features are:
</p>
<dl compact="compact">
<dt><span><code>"awt"</code></span></dt>
<dd><p>Abstract Window Toolkit for GUIs.
</p>
</dd>
<dt><span><code>"desktop"</code></span></dt>
<dd><p>Interactive desktop is running.
</p>
</dd>
<dt><span><code>"jvm"</code></span></dt>
<dd><p>Java Virtual Machine.
</p>
</dd>
<dt><span><code>"swing"</code></span></dt>
<dd><p>Swing components for lightweight GUIs.
</p></dd>
</dl>
<p><code>usejava</code> determines if specific Java features are available in an
Octave session. This function is provided for scripts which may alter
their behavior based on the availability of Java. The feature
<code>"desktop"</code> always returns <code>false</code> as Octave has no Java-based
desktop. Other features may be available if Octave was compiled with the
Java Interface and Java is installed.
</p>
<p><strong>See also:</strong> <a href="#XREFjavachk">javachk</a>.
</p></dd></dl>
<span id="index-memory_002c-displaying-Java-memory-status"></span>
<span id="XREFjavamem"></span><dl class="def">
<dt id="index-javamem"><span class="category">: </span><span><em></em> <strong>javamem</strong> <em>()</em><a href='#index-javamem' class='copiable-anchor'> ¶</a></span></dt>
<dt id="index-javamem-1"><span class="category">: </span><span><em><var>jmem</var> =</em> <strong>javamem</strong> <em>()</em><a href='#index-javamem-1' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>Show the current memory usage of the Java virtual machine (JVM) and run the
garbage collector.
</p>
<p>When no return argument is given the info is printed to the screen.
Otherwise, the output cell array <var>jmem</var> contains Maximum, Total, and
Free memory (in bytes).
</p>
<p>All Java-based routines are run in the JVM’s shared memory pool, a
dedicated and separate part of memory claimed by the JVM from your
computer’s total memory (which comprises physical RAM and virtual memory /
swap space on hard disk).
</p>
<p>The maximum allowable memory usage can be configured using the file
<samp>java.opts</samp>. The directory where this file resides is determined by
the environment variable <code><span class="nolinebreak">OCTAVE_JAVA_DIR</span></code><!-- /@w -->. If unset, the directory
where <samp>javaaddpath.m</samp> resides is used instead (typically
<samp><code><span class="nolinebreak">OCTAVE_HOME</span></code><!-- /@w -->/share/octave/<code><span class="nolinebreak">OCTAVE_VERSION</span></code><!-- /@w -->/m/java/</samp>).
</p>
<p><samp>java.opts</samp> is a plain text file with one option per line. The default
initial memory size and default maximum memory size (which are both system
dependent) can be overridden like so:
</p>
<p>-Xms64m
</p>
<p>-Xmx512m
</p>
<p>(in megabytes in this example).
You can adapt these values to your own requirements if your system has
limited available physical memory or if you get Java memory errors.
</p>
<p><code>"Total memory"</code> is what the operating system has currently assigned
to the JVM and depends on actual and active memory usage.
<code>"Free memory"</code> is self-explanatory. During operation of Java-based
Octave functions the amount of Total and Free memory will vary, due to
Java’s own cleaning up and your operating system’s memory management.
</p></dd></dl>
<span id="XREFjava_005fmatrix_005fautoconversion"></span><dl class="def">
<dt id="index-java_005fmatrix_005fautoconversion"><span class="category">: </span><span><em><var>val</var> =</em> <strong>java_matrix_autoconversion</strong> <em>()</em><a href='#index-java_005fmatrix_005fautoconversion' class='copiable-anchor'> ¶</a></span></dt>
<dt id="index-java_005fmatrix_005fautoconversion-1"><span class="category">: </span><span><em><var>old_val</var> =</em> <strong>java_matrix_autoconversion</strong> <em>(<var>new_val</var>)</em><a href='#index-java_005fmatrix_005fautoconversion-1' class='copiable-anchor'> ¶</a></span></dt>
<dt id="index-java_005fmatrix_005fautoconversion-2"><span class="category">: </span><span><em></em> <strong>java_matrix_autoconversion</strong> <em>(<var>new_val</var>, "local")</em><a href='#index-java_005fmatrix_005fautoconversion-2' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>Query or set the internal variable that controls whether Java arrays are
automatically converted to Octave matrices.
</p>
<p>The default value is false.
</p>
<p>When called from inside a function with the <code>"local"</code> option, the
variable is changed locally for the function and any subroutines it calls.
The original variable value is restored when exiting the function.
</p>
<p><strong>See also:</strong> <a href="#XREFjava_005funsigned_005fautoconversion">java_unsigned_autoconversion</a>, <a href="#XREFdebug_005fjava">debug_java</a>.
</p></dd></dl>
<span id="XREFjava_005funsigned_005fautoconversion"></span><dl class="def">
<dt id="index-java_005funsigned_005fautoconversion"><span class="category">: </span><span><em><var>val</var> =</em> <strong>java_unsigned_autoconversion</strong> <em>()</em><a href='#index-java_005funsigned_005fautoconversion' class='copiable-anchor'> ¶</a></span></dt>
<dt id="index-java_005funsigned_005fautoconversion-1"><span class="category">: </span><span><em><var>old_val</var> =</em> <strong>java_unsigned_autoconversion</strong> <em>(<var>new_val</var>)</em><a href='#index-java_005funsigned_005fautoconversion-1' class='copiable-anchor'> ¶</a></span></dt>
<dt id="index-java_005funsigned_005fautoconversion-2"><span class="category">: </span><span><em></em> <strong>java_unsigned_autoconversion</strong> <em>(<var>new_val</var>, "local")</em><a href='#index-java_005funsigned_005fautoconversion-2' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>Query or set the internal variable that controls how integer classes are
converted when <code>java_matrix_autoconversion</code> is enabled.
</p>
<p>When enabled, Java arrays of class Byte or Integer are converted to matrices
of class uint8 or uint32 respectively. The default value is true.
</p>
<p>When called from inside a function with the <code>"local"</code> option, the
variable is changed locally for the function and any subroutines it calls.
The original variable value is restored when exiting the function.
</p>
<p><strong>See also:</strong> <a href="#XREFjava_005fmatrix_005fautoconversion">java_matrix_autoconversion</a>, <a href="#XREFdebug_005fjava">debug_java</a>.
</p></dd></dl>
<span id="XREFdebug_005fjava"></span><dl class="def">
<dt id="index-debug_005fjava"><span class="category">: </span><span><em><var>val</var> =</em> <strong>debug_java</strong> <em>()</em><a href='#index-debug_005fjava' class='copiable-anchor'> ¶</a></span></dt>
<dt id="index-debug_005fjava-1"><span class="category">: </span><span><em><var>old_val</var> =</em> <strong>debug_java</strong> <em>(<var>new_val</var>)</em><a href='#index-debug_005fjava-1' class='copiable-anchor'> ¶</a></span></dt>
<dt id="index-debug_005fjava-2"><span class="category">: </span><span><em></em> <strong>debug_java</strong> <em>(<var>new_val</var>, "local")</em><a href='#index-debug_005fjava-2' class='copiable-anchor'> ¶</a></span></dt>
<dd><p>Query or set the internal variable that determines whether extra debugging
information regarding the initialization of the JVM and any Java exceptions
is printed.
</p>
<p>When called from inside a function with the <code>"local"</code> option, the
variable is changed locally for the function and any subroutines it calls.
The original variable value is restored when exiting the function.
</p>
<p><strong>See also:</strong> <a href="#XREFjava_005fmatrix_005fautoconversion">java_matrix_autoconversion</a>, <a href="#XREFjava_005funsigned_005fautoconversion">java_unsigned_autoconversion</a>.
</p></dd></dl>
</div>
<hr>
<div class="header">
<p>
Previous: <a href="Set-up-the-JVM.html">Set up the JVM</a>, Up: <a href="Java-Interface.html">Java Interface</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
</div>
</body>
</html>
|
