Multiple line code example in Javadoc comment

Enclose your multiline code with <pre></pre> tags.

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.

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>
...

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();