Coding Convention

Argument Assumption

• All method arguments are non-null unless explicitely stated otherwise in documentation.

<syntaxhighlight lang="java">

   /**
     * Read the object from a file.
     *
     * @param file 
     */
   void read(File file);

   /**
     * Write or remove existing value.
     *
     * @param newValue new value or null</t> to remove the existing value
     */
   void setValue(Object newValue);

</syntaxhighlight>

Non-null assumption applies in undocumented methods aswell. This method mustn't be called with a null argument.

<syntaxhighlight lang="java">

   void read(InputStream is);

</syntaxhighlight>

Return value assumption

• All return values are non-null unless explicitely stated otherwise in documentation.
  

<syntaxhighlight lang="java">

   /**
     * Get the value
     *
     * @return the value
     */
   Object get() throws ValueUnavailableException;

   /**
     * Get possibly existing value
     *
     * @return the value is exists, otherwise null
     */
   Object get();

</syntaxhighlight>

Non-null assumption applies in undocumented methods too, there is always a non-null return value.

<syntaxhighlight lang="java">

   Object get();

</syntaxhighlight>

Trust your assumptions

• You have a code of conduct - give it a chance.
  

The callee can trust the caller.

<syntaxhighlight lang="java">

   void read(InputStream is) {
       int  x = is.read();
   }

</syntaxhighlight>

And the caller the callee.

<syntaxhighlight lang="java">

   System.out.println( serialiser.deserialize( is ) ); 

</syntaxhighlight>

There is no need to do redundant checking, especially at run-time.

<syntaxhighlight lang="java">

   void read(InputStream is) {
       if ( is == null ) throw IllegalArgumentException("Non-null argument");
       int  x = is.read();
   } 

</syntaxhighlight>

Nor caller.

<syntaxhighlight lang="java">

   Object x = serializer.deserialize( is );
   if ( x != null ) System.out.println( x );

</syntaxhighlight>

Use assertions if you must. It sometimes improve quality and debuggability.

<syntaxhighlight lang="java" style="background: #dfd;">

   void read(InputStream is) {
       assert( is != null );
       int  x = is.read();
   }

</syntaxhighlight>

Return value assumption

All non-void methods return a non-null value unless expilitely stated otherwise in javadoc.