forked from ashishjohn1908/Java
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathmethods.html
More file actions
537 lines (505 loc) · 19.7 KB
/
Copy pathmethods.html
File metadata and controls
537 lines (505 loc) · 19.7 KB
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
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html lang="en-US" xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Defining Methods (The Java™ Tutorials >
Learning the Java Language > Classes and Objects)
</title>
<meta name="description" content="This beginner Java tutorial describes fundamentals of programming in the Java programming language" />
<meta name="keywords" content="java programming, learn java, java sample code, java objects, java classes, java inheritance, interfaces, variables, arrays, data types, operators, control flow, number, string" />
<style type="text/css">
.FigureCaption {
margin-left: 1in;
margin-right: 1in;
font-family: sans-serif;
font-size: smaller;
text-align: justify;
}
#TopBar_bl {
background: url(../../images/java_bar_bl.gif) 0 100% no-repeat;
width: 100%;
height: 60px;
}
#TopBar_br {
background: url(../../images/java_bar_br.gif) 100% 100% no-repeat;
width: 100%;
height: 60px;
}
#TopBar_tl {
background: url(../../images/java_bar_tl.gif) 0 0 no-repeat;
width: 100%;
height: 60px;
}
#TopBar_tr {
background: url(../../images/java_bar_tr.gif) 100% 0 no-repeat;
width: 100%;
height: 60px;
}
#TopBar {
background: #35556B url(../../images/java_bar.gif);
margin: 10px 10px 0 10px;
height:60px;
min-width:700px;
color: white;
font-family: sans-serif;
font-weight: bold;
}
@media print {
#BreadCrumbs, #Download {
display: none;
}
}
#TopBar_right {
line-height: 14px;
float: right;
padding-top: 2px;
padding-right: 30px;
text-align: left;
}
@media print {
#TopBar_right {
display: none;
}
}
#TopBar_right a {
font-size: 12px;
margin: 3px;
padding: 0;
}
#TopBar a:visited, #TopBar a:link {
color: white;
text-decoration: none;
}
#TopBar a:hover, #TopBar a:active {
background-color: white;
color: #35556B;
}
#BreadCrumbs {
padding: 4px 5px 0.5em 0;
font-family: sans-serif;
float: right;
}
#BreadCrumbs a {
color: blue;
}
#BreadCrumbs a:visited, #BreadCrumbs a:link {
text-decoration: none;
}
#BreadCrumbs a:hover, #BreadCrumbs a:active {
text-decoration: underline;
}
#PageTitle {
margin: 0 5px 0.5em 0;
color: #F90000;
}
#PageContent{
margin: 0 5px 0 20px;
}
.LeftBar_shown {
width: 13em;
float: left;
margin-left: 10px;
margin-top: 4px;
margin-bottom: 2em;
margin-right: 10px;
}
@media print {
.LeftBar_shown {
display: none;
}
}
.LeftBar_hidden {
display: none;
}
#Footer {
padding-top: 10px;
padding-left: 10px;
margin-right: 10px;
}
.footertext {
font-size: 10px;
font-family: sans-serif;
margin-top: 1px;
}
#Footer2 {
padding-top: 10px;
padding-left: 10px;
margin-right: 10px;
}
.NavBit {
padding: 4px 5px 0.5em 0;
font-family: sans-serif;
}
@media print {
.NavBit {
display: none;
}
}
#TagNotes {
text-align: right;
}
@media print {
#TagNotes a:visited, #TagNotes a:link {
color: #35556B;
text-decoration: none;
}
}
#Contents a, .NavBit a, #TagNotes a {
color: blue
}
#TagNotes a:visited, #TagNotes a:link,
#Contents a:visited, #Contents a:link,
.NavBit a:visited, .NavBit a:link {
text-decoration: none;
}
#TagNotes a:hover, #TagNotes a:active,
#Contents a:hover, #Contents a:active,
.NavBit a:hover, .NavBit a:active {
text-decoration: underline;
}
#Contents {
float: left;
font-family: sans-serif;
}
@media print {
#Contents {
display: none;
}
}
@media screen {
div.PrintHeaders {
display: none;
}
}
.linkLESSON, .nolinkLESSON {
margin-left: 0.5em;
text-indent: -0.5em
}
.linkAHEAD, .nolinkAHEAD, .linkQUESTIONS, .nolinkQUESTIONS {
margin-left: 1.5em;
text-indent: -0.5em
}
.linkBHEAD, .nolinkBHEAD {
margin-left: 2.5em;
text-indent: -0.5em
}
.linkCHEAD, .nolinkCHEAD {
margin-left: 3.5em;
text-indent: -0.5em
}
.nolinkLESSON, .nolinkAHEAD, .nolinkBHEAD, .nolinkCHEAD,
.nolinkQUESTIONS {
font-weight: bold;
color: #F90000;
}
.MainFlow_indented {
margin-right: 10px;
margin-left: 15em;
margin-bottom: 2em;
}
.MainFlow_wide {
margin-right: 10px;
margin-left: 10px;
margin-bottom: 2em;
}
@media print {
.MainFlow_indented, .MainFlow_wide {
padding-top: 0;
margin-top: 10px;
margin-right: 10px;
margin-left: 0;
}
}
h1, h2, h3, h4, h5 {
color: #F90000;
font-family: sans-serif;
}
h1 {
font-weight: bold;
font-size: 20px;
}
h2 {
font-weight: bold;
font-size: 17px;
}
h3 {
font-weight: bold;
font-size: 14px;
}
h4 {
font-size: 15px;
}
h5 {
font-size: 12px;
}
#ToggleLeft {
display: none;
}
.note {
margin: 0 30px 0px 30px;
}
.codeblock {
margin: 0 30px 0px 30px;
}
.tocli {
list-style-type:none;
}
.betadraft {
color: red;
}
</style>
<script type="text/javascript">
/* <![CDATA[ */
function leftBar() {
var nameq = 'tutorial_showLeftBar='
var cookies = document.cookie.split(';');
for (var i = 0; i < cookies.length; i++) {
var cookieString = cookies[i];
while (cookieString.charAt(0) == ' ') {
cookieString = cookieString.substring(1, cookieString.length);
}
if (cookieString.indexOf(nameq) == 0) {
cookieValue = cookieString.substring(nameq.length,
cookieString.length);
return cookieValue == 'yes';
}
}
return true;
}
function showLeft(b) {
var contents = document.getElementById("LeftBar");
var main = document.getElementById("MainFlow");
var toggle = document.getElementById("ToggleLeft");
if (b) {
contents.className = "LeftBar_shown";
main.className = "MainFlow_indented";
toggle.innerHTML = "Hide TOC";
document.cookie = 'tutorial_showLeftBar=yes; path=/';
} else {
contents.className = "LeftBar_hidden";
main.className = "MainFlow_wide";
toggle.innerHTML = "Show the TOC";
document.cookie = 'tutorial_showLeftBar=no; path=/';
}
}
function toggleLeft() {
showLeft(document.getElementById("LeftBar").className ==
"LeftBar_hidden");
document.getElementById("ToggleLeft").blur();
}
function load() {
showLeft(leftBar());
document.getElementById("ToggleLeft").style.display="inline";
}
function showCode(displayCodePage, codePath) {
var codePathEls = codePath.split("/");
var currDocPathEls = location.href.split("/");
//alert ("codePathEls = " + codePathEls + "\n" + "currDocPathEls = " + currDocPathEls);
currDocPathEls.pop(); // remove file name at the end
while (codePathEls.length > 0) {
if (codePathEls[0] == "..") {
codePathEls.shift();
currDocPathEls.pop();
} else {
break;
}
}
var fullCodePath = currDocPathEls.join("/") + "/" + codePathEls.join("/");
//alert ("fullCodePath = " + fullCodePath );
if (codePath.indexOf(".java") != -1 || codePath.indexOf(".jnlp") != -1) {
window.location.href = displayCodePage + "?code=" + encodeURI(fullCodePath);
} else {
window.location.href = fullCodePath;
}
}
/* ]]> */
</script>
</head>
<body onload="load()">
<noscript>
A browser with JavaScript enabled is required for this page to operate properly.
</noscript>
<div id="TopBar"> <div id="TopBar_tr"> <div id="TopBar_tl"> <div id="TopBar_br"> <div id="TopBar_bl">
<div id="TopBar_right">
<a target="_blank"
href="http://www.oracle.com/technetwork/java/javase/downloads/java-se-7-tutorial-2012-02-28-1536013.html">Download Ebooks</a><br />
<a target="_blank"
href="http://www.oracle.com/technetwork/java/javase/downloads/index.html">Download JDK</a>
<br />
<a href="../../search.html" target="_blank">Search Java Tutorials</a>
<br />
<a href="javascript:toggleLeft()"
id="ToggleLeft">Hide TOC</a>
</div>
</div> </div> </div> </div> </div>
<div class="PrintHeaders">
<b>Trail:</b> Learning the Java Language
<br /><b>Lesson:</b> Classes and Objects
<br /><b>Section:</b> Classes
</div>
<div id="LeftBar" class="LeftBar_shown">
<div id="Contents">
<div class="linkLESSON"><a href="index.html">Classes and Objects</a></div>
<div class="linkAHEAD"><a href="classes.html">Classes</a></div>
<div class="linkBHEAD"><a href="classdecl.html">Declaring Classes</a></div>
<div class="linkBHEAD"><a href="variables.html">Declaring Member Variables</a></div>
<div class="nolinkBHEAD">Defining Methods</div>
<div class="linkBHEAD"><a href="constructors.html">Providing Constructors for Your Classes</a></div>
<div class="linkBHEAD"><a href="arguments.html">Passing Information to a Method or a Constructor</a></div>
<div class="linkAHEAD"><a href="objects.html">Objects</a></div>
<div class="linkBHEAD"><a href="objectcreation.html">Creating Objects</a></div>
<div class="linkBHEAD"><a href="usingobject.html">Using Objects</a></div>
<div class="linkAHEAD"><a href="more.html">More on Classes</a></div>
<div class="linkBHEAD"><a href="returnvalue.html">Returning a Value from a Method</a></div>
<div class="linkBHEAD"><a href="thiskey.html">Using the this Keyword</a></div>
<div class="linkBHEAD"><a href="accesscontrol.html">Controlling Access to Members of a Class</a></div>
<div class="linkBHEAD"><a href="classvars.html">Understanding Class Members</a></div>
<div class="linkBHEAD"><a href="initial.html">Initializing Fields</a></div>
<div class="linkBHEAD"><a href="summaryclasses.html">Summary of Creating and Using Classes and Objects</a></div>
<div class="linkQUESTIONS"><a href="QandE/creating-questions.html">Questions and Exercises</a></div>
<div class="linkQUESTIONS"><a href="QandE/objects-questions.html">Questions and Exercises</a></div>
<div class="linkAHEAD"><a href="nested.html">Nested Classes</a></div>
<div class="linkBHEAD"><a href="innerclasses.html">Inner Class Example</a></div>
<div class="linkBHEAD"><a href="localclasses.html">Local Classes</a></div>
<div class="linkBHEAD"><a href="anonymousclasses.html">Anonymous Classes</a></div>
<div class="linkBHEAD"><a href="lambdaexpressions.html">Lambda Expressions</a></div>
<div class="linkCHEAD"><a href="methodreferences.html">Method References</a></div>
<div class="linkBHEAD"><a href="whentouse.html">When to Use Nested Classes, Local Classes, Anonymous Classes, and Lambda Expressions </a></div>
<div class="linkQUESTIONS"><a href="QandE/nested-questions.html">Questions and Exercises</a></div>
<div class="linkAHEAD"><a href="enum.html">Enum Types</a></div>
<div class="linkQUESTIONS"><a href="QandE/enum-questions.html">Questions and Exercises</a></div>
</div>
</div>
<div id="MainFlow" class="MainFlow_indented">
<span id="BreadCrumbs">
<a href="../../index.html" target="_top">Home Page</a>
>
<a href="../index.html" target="_top">Learning the Java Language</a>
>
<a href="index.html" target="_top">Classes and Objects</a>
</span>
<div class="NavBit">
<a target="_top" href="variables.html">« Previous</a> • <a target="_top" href="../TOC.html">Trail</a> • <a target="_top" href="constructors.html">Next »</a>
</div>
<div id="PageTitle"><h1>Defining Methods</h1></div>
<div id="PageContent">
<!---Defining Methods=-->
<p>Here is an example of a typical method declaration:</p>
<div class="codeblock"><pre>
public double calculateAnswer(double wingSpan, int numberOfEngines,
double length, double grossTons) {
//do the calculation here
}
</pre></div>
<p>The only required elements of a method declaration are the method's return type, name, a pair of parentheses, <code>()</code>, and a body between braces, <code>{}</code>.</p>
<p>More generally, method declarations have six components, in order:</p>
<ol>
<li>Modifiers—such as <code>public</code>, <code>private</code>, and others you will learn about later.</li>
<li>The return type—the data type of the value returned by the method, or <code>void</code> if the method does not return a value.</li>
<li>The method name—the rules for field names apply to method names as well, but the convention is a little different.</li>
<li>The parameter list in parenthesis—a comma-delimited list of input parameters, preceded by their data types, enclosed by parentheses, <code>()</code>. If there are no parameters, you must use empty parentheses.</li>
<li>An exception list—to be discussed later.</li>
<li>The method body, enclosed between braces—the method's code, including the declaration of local variables, goes here.</li>
</ol>
<p>Modifiers, return types, and parameters will be discussed later in this
lesson.
Exceptions are discussed in a later
lesson.
</p>
<div class="note"><hr /><strong>Definition:</strong> Two of the components of a method declaration comprise the <i>method signature</i>—the method's name and the parameter types.
<hr /></div>
<p>The signature of the method declared above is:</p>
<div class="codeblock"><pre>
calculateAnswer(double, int, double, double)
</pre></div>
<h2>Naming a Method</h2>
<p>Although a method name can be any legal identifier, code conventions restrict method names. By convention, method names should be a verb in lowercase or a multi-word name that begins with a verb in lowercase, followed by adjectives, nouns, etc. In multi-word names, the first letter of each of the second and following words should be capitalized. Here are some examples:</p>
<div class="codeblock"><pre>
run
runFast
getBackground
getFinalData
compareTo
setX
isEmpty
</pre></div>
<p>Typically, a method has a unique name within its class. However, a method might have the same name as other methods due to <i>method overloading</i>.</p>
<h2>Overloading Methods</h2>
<p>The Java programming language supports <i>overloading</i> methods, and Java can distinguish between methods with different <i>method signatures</i>. This means that methods within a class can have the same name if they have different parameter lists (there are some qualifications to this that will be discussed in
the lesson titled
"Interfaces and Inheritance").</p>
<p>Suppose that you have a class that can use calligraphy to draw various types of data (strings, integers, and so on) and that contains a method for drawing each data type. It is cumbersome to use a new name for each method—for example, <code>drawString</code>, <code>drawInteger</code>, <code>drawFloat</code>, and so on. In the Java programming language, you can use the same name for all the drawing methods but pass a different argument list to each method. Thus, the data drawing class might declare four methods named <code>draw</code>, each of which has a different parameter list.</p>
<div class="codeblock"><pre>
public class DataArtist {
...
public void draw(String s) {
...
}
public void draw(int i) {
...
}
public void draw(double f) {
...
}
public void draw(int i, double f) {
...
}
}
</pre></div>
<p>Overloaded methods are differentiated by the number and the type of the arguments passed into the method. In the code sample, <code>draw(String s)</code> and <code>draw(int i)</code> are distinct and unique methods because they require different argument types.</p>
<p>You cannot declare more than one method with the same name and the same number and type of arguments, because the compiler cannot tell them apart.</p>
<p>The compiler does not consider return type when differentiating methods, so you cannot declare two methods with the same signature even if they have a different return type.</p>
<div class="note"><hr /><strong>Note:</strong> Overloaded methods should be used sparingly, as they can make code much less readable.
<hr /></div>
</div>
<div class="NavBit">
<a target="_top" href="variables.html">« Previous</a>
•
<a target="_top" href="../TOC.html">Trail</a>
•
<a target="_top" href="constructors.html">Next »</a>
</div>
</div>
<div id="Footer2">
<hr />
<div id="TagNotes">
<p class="footertext">Problems with the examples? Try <a target="_blank"
href="../../information/run-examples.html">Compiling and Running
the Examples: FAQs</a>.
<br />
Complaints? Compliments? Suggestions? <a target="_blank"
href="http://docs.oracle.com/javase/feedback.html">Give
us your feedback</a>.
</p>
</div>
<div id="Footer">
<p class="footertext"><a name="license_info">Your use of this</a> page and all the material on pages under "The Java Tutorials" banner
is subject to these <a href="../../information/cpyr.html">legal notices</a>.
</p>
<table border="0" cellspacing="0" cellpadding="5" summary="">
<tr>
<td width="20%">
<table width="100%" border="0" cellspacing="0" cellpadding="5">
<tr>
<td headers="h1" align="center"><img id="duke" src="../../images/DukeWave.gif" width="55" height="55" alt="duke image" /></td>
<td headers="h2" align="left" valign="middle"><img id="oracle" src="../../images/logo_oracle_footer.gif" width="100" height="29" alt="Oracle logo" /></td>
</tr>
</table>
</td>
<td width="55%" valign="middle" align="center">
<p class="footertext"><a href="http://www.oracle.com/us/corporate/index.html">About Oracle</a> | <a href="http://www.oracle.com/technology/index.html">Oracle Technology Network</a> | <a href="http://www.oracle.com/us/legal/terms/index.html">Terms of Use</a></p>
</td>
<td width="25%" valign="middle" align="right">
<p class="footertext">Copyright © 1995, 2014 Oracle and/or its affiliates. All rights reserved.</p>
</td>
</tr>
</table>
</div>
</div>
<div class="PrintHeaders">
<b>Previous page:</b> Declaring Member Variables
<br /><b>Next page:</b> Providing Constructors for Your Classes
</div>
</body>
</html>