Stuart Halloway of Relevance has recently published a series of articles on his blog regarding Myths of Ruby vs Java. He has experience of working with both the technologies so his views may be interested for anyone. Although I don’t have working experience of Java but still the articles are useful. As a conclusion he has said that Ruby is great as a language and Java is great as a platform so the best way is to use JRuby. Have a look on the articles. Ruby vs. Java Myth #1: Project Size
Ruby vs. Java Myth #2: Ruby feature X makes code unmaintainable
Ruby vs. Java Myth #3: Ruby is too hard