Month: December 2011

Collection classes in Java

Collections are very important on SCJP exam. It’s useful to remember the following…

List

• ordered (index)
• duplicates allowed

ArrayList

• fast iteration
• fast random access; as of Java 1.4 implements RandomAccess interface
• slower instertion and deletion

Vector

• the same as ArrayList but its metods are synchronized (therefore slower)

LinkedList

• elements are doubly linked to one another; linkage adds methods that allow

Assertions in Java

assert Expression1 : Expression2;

• Expression1 is asserted to be true; otherwise AssertionError (that shouldn’t be handled) is thrown
• Expression2 allows to produce some additional information
• Expression2 MUST result in a value – it generates a String message
• allow testing during the development and debugging
• are disabled at runtime by default
• can be enabled using -ea or -enableassertions flags and selectively