Related
I have a small code example I want to include in the Javadoc comment for a method.
/**
* -- ex: looping through List of Map objects --
* <code>
* for (int i = 0; i < list.size(); i++) {
* Map map = (Map)list.get(i);
* System.out.println(map.get("wordID"));
* System.out.println(map.get("word"));
* }
* </code>
*
* #param query - select statement
* #return List of Map objects
*/
The problem is the code example shows up in the Javadoc with no line breaks making it hard to read.
-- ex: looping through List of Map objects -- for (int i = 0; i list.size(); i++) { Map map = (Map)list.get(i); System.out.println(map.get("wordID")); System.out.println(map.get("word")); }
Parameters
query - - select statement
Returns:
List of Map objects
I guess I am wrong in assuming the code tag would handle line breaks. What is the best way to format code examples in Javadoc comments ?
In addition to the already mentioned <pre> tags, you should also use the #code JavaDoc annotation, which will make life much easier when it comes to HTML entities issues (in particular with Generics), e.g.:
* <pre>
* {#code
* Set<String> s;
* System.out.println(s);
* }
* </pre>
Will give correct HTML output:
Set<String> s;
System.out.println(s);
While omitting the #code block (or using a <code> tag) will result in HTML like this:
Set s;
System.out.println(s);
For reference, a full list of tag descriptions available in Java SE 8 can be found here.
I had a really tough time with including a specific code example in a javadoc comment. I'd like to share this one.
Please note the following:
usage of old <code> - tag to prevent the curly brackets from being interpreted
usage of "new" {#code ...} - tag to get the generics included in the output
escaping of the # sign in #Override via "{#literal #}Override" because javadoc generator "tilts" there due to the fact that the # goes directly after an opening curly bracket
remove one space in front of {#code and {#literal, to compensate inner spaces and keep the alignment
javadoc code:
/** this methods adds a specific translator from one type to another type. `
* i.e.
* <pre>
* <code>new BeanTranslator.Builder()
* .translate(
* new{#code Translator<String, Integer>}(String.class, Integer.class){
* {#literal #}Override
* public Integer translate(String instance) {
* return Integer.valueOf(instance);
* }})
* .build();
* </code>
* </pre>
* #param translator
*/
gets printed as
new BeanTranslator.Builder()
.translate(
new Translator<String, Integer>(String.class, Integer.class){
#Override
public Integer translate(String instance) {
return Integer.valueOf(instance);
}})
.build();
The java source has lots of good examples for this. Here's an example from the head of "String.java":
....
* is equivalent to:
* <p><blockquote><pre>
* char data[] = {'a', 'b', 'c'};
* String str = new String(data);
* </pre></blockquote><p>
* Here are some more examples of how strings can be used:
* <p><blockquote><pre>
* System.out.println("abc");
* String cde = "cde";
* System.out.println("abc" + cde);
* String c = "abc".substring(2,3);
* String d = cde.substring(1, 2);
* </pre></blockquote>
...
Enclose your multiline code with <pre></pre> tags.
You need the <pre></pre> tags for the line breaks, and the {#code ... } inside them for generics. But then it's not allowed to place the opening brace on the same line as the <generic> tag, because then everything will be displayed on 1 line again.
Displays on one line:
* ..
* <pre>
* {#code
* public List<Object> getObjects() {
* return objects;
* }
* </pre>
* ..
Displays with line breaks:
* ..
* <pre>
* {#code
* public List<Object> getObjects()
* {
* return objects;
* }
* </pre>
* ..
Another weird thing is when you paste the closing brace of {#code, it gets displayed:
* ..
* <pre>
* {#code
* public List<Object> getObjects()
* {
* return objects;
* }
* }
* </pre>
* ..
Output:
public List<Object> getObjects()
{
return objects;
}
}
/**
* <blockquote><pre>
* {#code
* public Foo(final Class<?> klass) {
* super();
* this.klass = klass;
* }
* }
* </pre></blockquote>
**/
<pre/> is required for preserving lines.
{#code must has its own line
<blockquote/> is just for indentation.
public Foo(final Class<?> klass) {
super();
this.klass = klass;
}
UPDATE with JDK8
The minimum requirements for proper codes are <pre/> and {#code}.
/**
* test.
*
* <pre>{#code
* <T> void test(Class<? super T> type) {
* System.out.printf("hello, world\n");
* }
* }</pre>
*/
yields
<T> void test(Class<? super T> type) {
System.out.printf("hello, world\n");
}
And an optional surrounding <blockquote/> inserts an indentation.
/**
* test.
*
* <blockquote><pre>{#code
* <T> void test(Class<? super T> type) {
* System.out.printf("hello, world\n");
* }
* }</pre></blockquote>
*/
yields
<T> void test(Class<? super T> type) {
System.out.printf("hello, world\n");
}
Inserting <p> or surrounding with <p> and </p> yields warnings.
Here's my two cents.
As the other answers already state, you should use <pre> </pre> in conjuction with {#code }.
Use pre and {#code}
Wrapping your code inside <pre> and </pre> prevents your code from collapsing onto one line;
Wrapping your code inside {#code } prevents <, > and everything in between from disappearing. This is particularly useful when your code contains generics or lambda expressions.
Problems with annotations
Problems can arise when your code block contains an annotation. That is probably because when the # sign appears at the beginning of the Javadoc line, it is considered a Javadoc tag like #param or #return. For example, this code could be parsed incorrectly:
/**
* Example usage:
*
* <pre>{#code
* #Override
* public void someOverriddenMethod() {
Above code will disappear completely in my case.
To fix this, the line must not start with an # sign:
/**
* Example usage:
*
* <pre>{#code #Override
* public int someMethod() {
* return 13 + 37;
* }
* }</pre>
*/
Note that there are two spaces between #code and #Override, to keep things aligned with the next lines. In my case (using Apache Netbeans) it is rendered correctly.
I was able to generate good looking HTML files with the following snip-it shown in Code 1.
* <pre>
* {#code
* A-->B
* \
* C-->D
* \ \
* G E-->F
* }
*</pre>
(Code 1)
Code 1 turned into the generated javadoc HTML page in Fig 1, as expected.
A-->B
\
C-->D
\ \
G E-->F
(Fig. 1)
However, in NetBeans 7.2, if you hit Alt+Shift+F (to reformat the current file), Code 1 turns in to Code 2.
* <
* pre>
* {#code
* A-->B
* \
* C-->D
* \ \
* G E-->F
* }
* </pre>
(Code 2)
where the first <pre> is now broken onto two lines. Code 2 produces generated javadoc HTML file as shown in Fig 2.
< pre> A-->B \ C-->D \ \ G E-->F
(Fig 2)
Steve B's suggestion (Code 3) seems to give the best results and remains formatted as expected even after hitting Alt+Shift+F.
*<p><blockquote><pre>
* A-->B
* \
* C-->D
* \ \
* G E-->F
* </pre></blockquote>
(Code 3)
Use of Code 3 produces the same javadoc HTML output as shown in Fig 1.
Since Java 18 (JEP 413) you may use #snippet tag:
/**
* -- ex: looping through List of Map objects --
* {#snippet :
* for (int i = 0; i < list.size(); i++) {
* Map map = (Map)list.get(i);
* System.out.println(map.get("wordID"));
* System.out.println(map.get("word"));
* }
* }
*
* #param query - select statement
* #return List of Map objects
*/
There is a significant difference between <blockquote><pre>... and <pre>{#code.... The former will omit the type declarations in generics but the latter will keep it.
E.g.:
List<MyClass> myObject = null;
displays as List myObject = null; with the firts and as List<MyClass> myObject = null; with the second
I just read the Javadoc 1.5 reference here, and only the code with <and > must be enclosed inside {#code ...}. Here a simple example:
/**
* Bla bla bla, for example:
*
* <pre>
* void X() {
* List{#code <String>} a = ...;
* ...
* }
* </pre>
*
* #param ...
* #return ...
*/
.... your code then goes here ...
A combination of two of the other solutions seems perfect:
* <pre>{#code
* {#literal #}Override
* public void someMethod() {
* Set<String> s;
* }
* }</pre>
ie. use <pre>{#code to start and }</pre> to end the snippet. Also, replace # with {#literal #}.
Haven't found an easier solution. Quite sad for a language that has been under active development for decades.
If you are Android developer you can use:
<pre class=”prettyprint”>
TODO:your code.
</pre>
To pretty print your code in Javadoc with Java code.
Try replacing "code" with "pre". The pre tag in HTML marks the text as preformatted and all linefeeds and spaces will appear exactly as you type them.
I work through these two ways without any problem:
<pre>
<code>
... java code, even including annotations
</code>
</pre>
and
<pre class="code">
... java code, even including annotations
</pre>
Of course the latter is more simplest and observe the class="code" part
I enclose my example code with <pre class="brush: java"></pre> tags and use SyntaxHighlighter for published javadocs. It doesn't hurt IDE and makes published code examples beautiful.
Using Java SE 1.6, it looks like all UPPERCASE PRE identifiers is the best way to do this in Javadoc:
/**
* <PRE>
* insert code as you would anywhere else
* </PRE>
*/
is the simplest way to do this.
An Example from a javadoc I got from a java.awt.Event method:
/**
* <PRE>
* int onmask = SHIFT_DOWN_MASK | BUTTON1_DOWN_MASK;
* int offmask = CTRL_DOWN_MASK;
* if ((event.getModifiersEx() & (onmask | offmask)) == onmask) {
* ...
* }
* </PRE>
*/
This produces output that looks exactly like the regular code, with the regular code spacings and new lines intact.
In Visual Studio Code at least, you can force a Javadoc comment to respect line-breaks by wrapping it in triple-backticks, as seen below:
/** ```markdown
* This content is rendered in (partial) markdown.
*
* For example, *italic* and **bold** text works, but [links](https://www.google.com) do not.
* Bonus: it keeps single line-breaks, as seen between this line and the previous.
``` */
I'm making javadoc:
/**
* make Something
*
* #param value - blabla( I´m using #param value - blabla, instead #param
* value blabla)
* #return something
*/
public String makeSomething(String value) {
return "";
}
Should I use #param value - or just #param value?
Most doclets introduce a hypen between the #param tag and the parameter's name. Adding another hypen yourself will cause an ugly, double hypen to be rendered.
I'm compiling my java project with java 4 using GNU Make which does not support generics.
Here's my little code causing the error :
for (int i = 0; i < text.length(); i++) {
if (text.charAt(i) > 127) {
buffer.append("\"");
String charValue = asciiToNascMap.get(String.valueOf((int)text.charAt(i)));
buffer.append(String.format(";CHR$(%d);\"", charValue));
} else {
buffer.append(text.charAt(i));
}
}
private static Map<String, String> asciiToNascMap = new HashMap<String, String>();
static {
asciiToNascMap.put("232", "125");//è
asciiToNascMap.put("233", "123");//é
asciiToNascMap.put("224", "64");//à
asciiToNascMap.put("231", "92");//ç
asciiToNascMap.put("199", "180");//Ç
asciiToNascMap.put("234", "193");//ê
}
I'm getting this error :
Printer.java:319: error:Cannot find method "java/lang/String.format(java.lang.String, java.lang.String)"
Here's the signature of the String.format method :
/**
* Returns a formatted string using the specified format string and
* arguments.
*
* <p> The locale always used is the one returned by {#link
* java.util.Locale#getDefault() Locale.getDefault()}.
*
* #param format
* A format string
*
* #param args
* Arguments referenced by the format specifiers in the format
* string. If there are more arguments than format specifiers, the
* extra arguments are ignored. The number of arguments is
* variable and may be zero. The maximum number of arguments is
* limited by the maximum dimension of a Java array as defined by
* <cite>The Java™ Virtual Machine Specification</cite>.
* The behaviour on a
* <tt>null</tt> argument depends on the <a
* href="../util/Formatter.html#syntax">conversion</a>.
*
* #throws IllegalFormatException
* If a format string contains an illegal syntax, a format
* specifier that is incompatible with the given arguments,
* insufficient arguments given the format string, or other
* illegal conditions. For specification of all possible
* formatting errors, see the <a
* href="../util/Formatter.html#detail">Details</a> section of the
* formatter class specification.
*
* #throws NullPointerException
* If the <tt>format</tt> is <tt>null</tt>
*
* #return A formatted string
*
* #see java.util.Formatter
* #since 1.5
*/
public static String format(String format, Object ... args) {
return new Formatter().format(format, args).toString();
}
The method you are trying to use is not available in Java 1.4. See the #since tag in your posted commentary. It says #since 1.5 meaning it was intoduced in Java 1.5.
You cannot use String.format in Java 1.4.
Try:
buffer.append(";CHR$(").append(Integer.valueOf(charValue)).append(");\"");
String.format is not available in Java 1.4. This is indicated in the text you posted in the #since tag. varargs support was not added until Java 5, which is why it probably wasn't added until then. People have created C printf-style libraries, however.
See these links:
http://www.sharkysoft.com/archive/printf/docs/javadocs/lava/clib/stdio/doc-files/introduction.htm
http://www.cs.ubc.ca/~lloyd/java/doc/cformat.html
How can I format headings in a javadoc comment such that they match the format of #param, #return, or #throws. I am not asking how to define my own keywords rather how to heave a bold face heading similar to them.
I have tried <h1></h1> but it looks terrible in the Javadoc-view of Eclipse, in particular the size is much larger. Is there an alternative or is <h1></h1> the way to go?
/**
* foo
*
* #param x foo
* #return foo
* #throws foo
*/
public int foo(int x) { return x; }
The screenshot is from taken from Eclipse.
Update
I do not think that <strong> is sufficient, since it does not add line breaks:
/**
* Introdcution
*
* <strong>Heading</strong>There is no line break.
* <strong>Heading</strong>There is no line break.
*
* #param x foo
* #return foo
* #throws foo
*/
Just have a look at the generated Java Doc of the JAVA API, e.g. SimpleDateFormat.parse (have a look at the HTML source code).
They use a html description list for formatting and a strong CSS class to format the term. So do it the same:
/**
* Introdcution
*
* <dl>
* <dt><span class="strong">Heading 1</span></dt><dd>There is a line break.</dd>
* <dt><span class="strong">Heading 2</span></dt><dd>There is a line break.</dd>
* </dl>
*
* #param x foo
* #return foo
* #throws foo
*/
Looks like this:
Use:
/**
* <strong>Heading</strong>There is no line break.
* <br /> <strong>Heading</strong>There is no line break.
*
* #param x foo
* #return foo
* #throws foo
*/
public int foo(int x) { return x; }
I have a small code example I want to include in the Javadoc comment for a method.
/**
* -- ex: looping through List of Map objects --
* <code>
* for (int i = 0; i < list.size(); i++) {
* Map map = (Map)list.get(i);
* System.out.println(map.get("wordID"));
* System.out.println(map.get("word"));
* }
* </code>
*
* #param query - select statement
* #return List of Map objects
*/
The problem is the code example shows up in the Javadoc with no line breaks making it hard to read.
-- ex: looping through List of Map objects -- for (int i = 0; i list.size(); i++) { Map map = (Map)list.get(i); System.out.println(map.get("wordID")); System.out.println(map.get("word")); }
Parameters
query - - select statement
Returns:
List of Map objects
I guess I am wrong in assuming the code tag would handle line breaks. What is the best way to format code examples in Javadoc comments ?
In addition to the already mentioned <pre> tags, you should also use the #code JavaDoc annotation, which will make life much easier when it comes to HTML entities issues (in particular with Generics), e.g.:
* <pre>
* {#code
* Set<String> s;
* System.out.println(s);
* }
* </pre>
Will give correct HTML output:
Set<String> s;
System.out.println(s);
While omitting the #code block (or using a <code> tag) will result in HTML like this:
Set s;
System.out.println(s);
For reference, a full list of tag descriptions available in Java SE 8 can be found here.
I had a really tough time with including a specific code example in a javadoc comment. I'd like to share this one.
Please note the following:
usage of old <code> - tag to prevent the curly brackets from being interpreted
usage of "new" {#code ...} - tag to get the generics included in the output
escaping of the # sign in #Override via "{#literal #}Override" because javadoc generator "tilts" there due to the fact that the # goes directly after an opening curly bracket
remove one space in front of {#code and {#literal, to compensate inner spaces and keep the alignment
javadoc code:
/** this methods adds a specific translator from one type to another type. `
* i.e.
* <pre>
* <code>new BeanTranslator.Builder()
* .translate(
* new{#code Translator<String, Integer>}(String.class, Integer.class){
* {#literal #}Override
* public Integer translate(String instance) {
* return Integer.valueOf(instance);
* }})
* .build();
* </code>
* </pre>
* #param translator
*/
gets printed as
new BeanTranslator.Builder()
.translate(
new Translator<String, Integer>(String.class, Integer.class){
#Override
public Integer translate(String instance) {
return Integer.valueOf(instance);
}})
.build();
The java source has lots of good examples for this. Here's an example from the head of "String.java":
....
* is equivalent to:
* <p><blockquote><pre>
* char data[] = {'a', 'b', 'c'};
* String str = new String(data);
* </pre></blockquote><p>
* Here are some more examples of how strings can be used:
* <p><blockquote><pre>
* System.out.println("abc");
* String cde = "cde";
* System.out.println("abc" + cde);
* String c = "abc".substring(2,3);
* String d = cde.substring(1, 2);
* </pre></blockquote>
...
Enclose your multiline code with <pre></pre> tags.
You need the <pre></pre> tags for the line breaks, and the {#code ... } inside them for generics. But then it's not allowed to place the opening brace on the same line as the <generic> tag, because then everything will be displayed on 1 line again.
Displays on one line:
* ..
* <pre>
* {#code
* public List<Object> getObjects() {
* return objects;
* }
* </pre>
* ..
Displays with line breaks:
* ..
* <pre>
* {#code
* public List<Object> getObjects()
* {
* return objects;
* }
* </pre>
* ..
Another weird thing is when you paste the closing brace of {#code, it gets displayed:
* ..
* <pre>
* {#code
* public List<Object> getObjects()
* {
* return objects;
* }
* }
* </pre>
* ..
Output:
public List<Object> getObjects()
{
return objects;
}
}
/**
* <blockquote><pre>
* {#code
* public Foo(final Class<?> klass) {
* super();
* this.klass = klass;
* }
* }
* </pre></blockquote>
**/
<pre/> is required for preserving lines.
{#code must has its own line
<blockquote/> is just for indentation.
public Foo(final Class<?> klass) {
super();
this.klass = klass;
}
UPDATE with JDK8
The minimum requirements for proper codes are <pre/> and {#code}.
/**
* test.
*
* <pre>{#code
* <T> void test(Class<? super T> type) {
* System.out.printf("hello, world\n");
* }
* }</pre>
*/
yields
<T> void test(Class<? super T> type) {
System.out.printf("hello, world\n");
}
And an optional surrounding <blockquote/> inserts an indentation.
/**
* test.
*
* <blockquote><pre>{#code
* <T> void test(Class<? super T> type) {
* System.out.printf("hello, world\n");
* }
* }</pre></blockquote>
*/
yields
<T> void test(Class<? super T> type) {
System.out.printf("hello, world\n");
}
Inserting <p> or surrounding with <p> and </p> yields warnings.
Here's my two cents.
As the other answers already state, you should use <pre> </pre> in conjuction with {#code }.
Use pre and {#code}
Wrapping your code inside <pre> and </pre> prevents your code from collapsing onto one line;
Wrapping your code inside {#code } prevents <, > and everything in between from disappearing. This is particularly useful when your code contains generics or lambda expressions.
Problems with annotations
Problems can arise when your code block contains an annotation. That is probably because when the # sign appears at the beginning of the Javadoc line, it is considered a Javadoc tag like #param or #return. For example, this code could be parsed incorrectly:
/**
* Example usage:
*
* <pre>{#code
* #Override
* public void someOverriddenMethod() {
Above code will disappear completely in my case.
To fix this, the line must not start with an # sign:
/**
* Example usage:
*
* <pre>{#code #Override
* public int someMethod() {
* return 13 + 37;
* }
* }</pre>
*/
Note that there are two spaces between #code and #Override, to keep things aligned with the next lines. In my case (using Apache Netbeans) it is rendered correctly.
I was able to generate good looking HTML files with the following snip-it shown in Code 1.
* <pre>
* {#code
* A-->B
* \
* C-->D
* \ \
* G E-->F
* }
*</pre>
(Code 1)
Code 1 turned into the generated javadoc HTML page in Fig 1, as expected.
A-->B
\
C-->D
\ \
G E-->F
(Fig. 1)
However, in NetBeans 7.2, if you hit Alt+Shift+F (to reformat the current file), Code 1 turns in to Code 2.
* <
* pre>
* {#code
* A-->B
* \
* C-->D
* \ \
* G E-->F
* }
* </pre>
(Code 2)
where the first <pre> is now broken onto two lines. Code 2 produces generated javadoc HTML file as shown in Fig 2.
< pre> A-->B \ C-->D \ \ G E-->F
(Fig 2)
Steve B's suggestion (Code 3) seems to give the best results and remains formatted as expected even after hitting Alt+Shift+F.
*<p><blockquote><pre>
* A-->B
* \
* C-->D
* \ \
* G E-->F
* </pre></blockquote>
(Code 3)
Use of Code 3 produces the same javadoc HTML output as shown in Fig 1.
Since Java 18 (JEP 413) you may use #snippet tag:
/**
* -- ex: looping through List of Map objects --
* {#snippet :
* for (int i = 0; i < list.size(); i++) {
* Map map = (Map)list.get(i);
* System.out.println(map.get("wordID"));
* System.out.println(map.get("word"));
* }
* }
*
* #param query - select statement
* #return List of Map objects
*/
There is a significant difference between <blockquote><pre>... and <pre>{#code.... The former will omit the type declarations in generics but the latter will keep it.
E.g.:
List<MyClass> myObject = null;
displays as List myObject = null; with the firts and as List<MyClass> myObject = null; with the second
I just read the Javadoc 1.5 reference here, and only the code with <and > must be enclosed inside {#code ...}. Here a simple example:
/**
* Bla bla bla, for example:
*
* <pre>
* void X() {
* List{#code <String>} a = ...;
* ...
* }
* </pre>
*
* #param ...
* #return ...
*/
.... your code then goes here ...
A combination of two of the other solutions seems perfect:
* <pre>{#code
* {#literal #}Override
* public void someMethod() {
* Set<String> s;
* }
* }</pre>
ie. use <pre>{#code to start and }</pre> to end the snippet. Also, replace # with {#literal #}.
Haven't found an easier solution. Quite sad for a language that has been under active development for decades.
If you are Android developer you can use:
<pre class=”prettyprint”>
TODO:your code.
</pre>
To pretty print your code in Javadoc with Java code.
Try replacing "code" with "pre". The pre tag in HTML marks the text as preformatted and all linefeeds and spaces will appear exactly as you type them.
I work through these two ways without any problem:
<pre>
<code>
... java code, even including annotations
</code>
</pre>
and
<pre class="code">
... java code, even including annotations
</pre>
Of course the latter is more simplest and observe the class="code" part
I enclose my example code with <pre class="brush: java"></pre> tags and use SyntaxHighlighter for published javadocs. It doesn't hurt IDE and makes published code examples beautiful.
Using Java SE 1.6, it looks like all UPPERCASE PRE identifiers is the best way to do this in Javadoc:
/**
* <PRE>
* insert code as you would anywhere else
* </PRE>
*/
is the simplest way to do this.
An Example from a javadoc I got from a java.awt.Event method:
/**
* <PRE>
* int onmask = SHIFT_DOWN_MASK | BUTTON1_DOWN_MASK;
* int offmask = CTRL_DOWN_MASK;
* if ((event.getModifiersEx() & (onmask | offmask)) == onmask) {
* ...
* }
* </PRE>
*/
This produces output that looks exactly like the regular code, with the regular code spacings and new lines intact.
In Visual Studio Code at least, you can force a Javadoc comment to respect line-breaks by wrapping it in triple-backticks, as seen below:
/** ```markdown
* This content is rendered in (partial) markdown.
*
* For example, *italic* and **bold** text works, but [links](https://www.google.com) do not.
* Bonus: it keeps single line-breaks, as seen between this line and the previous.
``` */