I have been thinking again, about multiple inheritance and why Java doesn't support it. I wrote a bit about this topic, some time ago.
There are so, so many resources on web about this, and it's actually very easy to find the answer to this, via a simple web search. Here is an article from where I started to know an answer to this, http://www.javaworld.com/javaqa/2002-07/02-qa-0719-multinheritance.html, which pointed me to this white paper by James Gosling and Henry McGilton. Really, I did not read this white paper by Java creators earlier (it never came across my eyes :)), in spite being familiar and working with Java since long time. Sometimes, we find gems on web in an unexpected ways (I mean, this paper is a gem for me :)). I'll try to read this paper (hopefully fully, and being able to understand it) over the next few days.
And here is a link in this white paper, which explains why Java doesn't support multiple inheritance. The following white paper link is also interesting, which gives a complete overview of C and C++ features, that were omitted in Java language (Java has been influenced from C and C++).
My personal opinion is, that if we must need to use multiple inheritance, we should just try to write programs in C++. On the contrary, my experience in using Java for about a decade, convinces me, that Java is suitable to solve almost any business application problem, and absence of multiple inheritance in Java, is not an hindrance to design good programming abstractions for problem domain. The advantages like Java's byte code portability and web friendliness far outweigh, any disadvantages caused by absence of multiple inheritance. On numerous occasions, I have created Java byte code on Windows, and used it without modification on Unix based systems (and vice versa). This is something which is built into the Java language, and it is cool!