I had posted this very question long time ago, but I wasn't clear with my question. Well, I wanted to know which methods I ought to study from the String, StringBuffer, Thread, and the Collections Framework. Sun is very clear about which methods I need to know from the Math and Wrapper classes but does not state much for the classes String, StringBuffer, and Thread. There are a lot of methods from these classes which I have never used. Which methods should I study from the three classes I mentioned and the collections framework?
"Which methods should I study from the three classes I mentioned and the collections framework?"
The easy answer is all of them.
Here's the practical answer that will cover most of the questions:
For collections know how each collection is used and which is best for a given situation.
For StringBuffer, know that this class does not ovveride equals() and that class methods that alter this StringBuffer and return StringBuffer return and alter itself.
For String, know that equals() lexicographically compares two strings and that class methods that seem to change strings leave the invoking String unchanged and return a new String; in short, internalize that Strings are immutable.
(To illustrate an important difference between the StringBuffer and String methods, understand what is going on with, e.g., StringBuffer.append(StringBuffer sb) and String.concat(String str).)