Java collections framework class and interface hierarchy, excluding types in the java.util.concurrent package and a few other classes
The Java collections framework is a set of classes and interfaces that implement commonly reusable collection data structures (collections).
Although referred to as a framework, it works in a manner of a library. The collections framework provides both interfaces that define various collections and classes that implement them.
java.lang.Long, or Collection instead of an array prevents run time exceptions by instead throwing a compile-time exception to inform the developer to fix the code. For example, if a developer declares an Long[] instance with a certain capacity, no compile-time exception will be thrown. If the developer attempts to add a ArrayStoreException. On the other hand, if the developer instead declared a new instance of a "},"parts":[{"template":{"target":{"wt":"code","href":"./Template:Code"},"params":{"1":{"wt":"Collection<Object>"}},"i":0}}]}'>Collection<Object> as "},"parts":[{"template":{"target":{"wt":"code","href":"./Template:Code"},"params":{"1":{"wt":"ArrayList<Long>"}},"i":0}}]}'>ArrayList<Long>, the Java compiler will (correctly) throw a compile-time exception to indicate that the code is written with incompatible and incorrect type, thus preventing any potential run-time exceptions.The developer can fix the code by instantianting "},"parts":[{"template":{"target":{"wt":"code","href":"./Template:Code"},"params":{"1":{"wt":"Collection<Object>"}},"i":0}}]}'>Collection<Object> as an "},"parts":[{"template":{"target":{"wt":"code","href":"./Template:Code"},"params":{"1":{"wt":"ArrayList<Object>"}},"i":0}}]}'>ArrayList<Object> object. If the code is using Java SE7 or later versions, the developer can instantiate "},"parts":[{"template":{"target":{"wt":"code","href":"./Template:Code"},"params":{"1":{"wt":"Collection<Object>"}},"i":0}}]}'>Collection<Object> as an "},"parts":[{"template":{"target":{"wt":"code","href":"./Template:Code"},"params":{"1":{"wt":"ArrayList<>"}},"i":0}}]}'>ArrayList<> object by using the diamond operatorCollections are generic and hence reified, but arrays are not reified.
History
editCollection implementations in pre-JDK 1.2 versions of the Java platform included few data structure classes, but did not contain a collections framework. The standard methods for grouping Java objects were via the array, the Vector, and the Hashtable classes, which unfortunately were not easy to extend, and did not implement a standard member interface.add(E e) and contains(E e) method checks if a specified element exists in the Collection.
The Collection interface is a subinterface of java.util.Iterator to scan all of the elements in the Collection.
Collection is generic. Any Collection can store any String objects. No casting is required when using the AbstractList and all of its corresponding subclasses, as well as AbstractList class include Vector.
java.util.ArrayList class implements the List as an array. Whenever functions specific to a List are required, the class moves the elements around within the array in order to do it.
Vector class
editThe Stack classedit
The java.util.Stack. The Stack offers methods to put a new object on the Stack (method push(E e) and empty()), and a method to search the Stack for an item and discover how far it is from the top (CopyOnWriteArrayList extends the CopyOnWriteArrayList should not be used.
However synchronization can incur a performance overhead. For scenarios where synchronization is not mandatory, then the java.util.Queue interface defines the queue data structure, which stores elements in the order in which they are inserted. New additions go to the end of the line, and elements are removed from the front. It creates a first-in first-out system. This interface is implemented by java.util.LinkedList, Queue implementationsedit
