> StringBuffer java.lang.StringBuffer.append(String str)
> Appends the specified string to this character sequence. [...] If str is null, then the four characters "null" are appended.

so I guess
``` java 
stringBuffer.append(args[i]);
```
would do the same as 
``` java
if (args[i] == null) {
	stringBuffer.append("null");
} else {
	stringBuffer.append(args[i].toString());
}
```