Java Vector Tutorial

Java Vector is a resizable array of Objects which implements the List interface (As of JDK 1.2, Java Vector is retrofitted to implement List interface, and thus became a part of Java Collection framework). Like an array, elements of the Java Vector can be accessed using an index.

Java Vector is similar to Java ArrayList, but it is synchronized.

Java Vector Capacity

Capacity of the Java Vector is the actual size of the array used to store the elements. It is usually larger than the size of the Vector. When more components are added to the Vector, its size is increased by the size of capacityIncrement.

Program should increase the capacity of Vector before inserting large number of elements to the Vector. It reduces the number of reallocations Vector has to make to fit the elements and thus improves the overall performance.

We can increase the capacity of the Vector using following method.

Vector v = new Vector();
v.ensureCapacity(80);

Java Vector Iterators

Vector provides two types of Iterators.
1) Iterator
2) ListIterator

Using following methods.

Iterator iterator = v.iterator();

Returns Iterator object.

ListIterator listIterator = v.listIterator();

Returns Object of ListIterator.

ListIterator listIterator = v.listIterator(int startIndex);

Returns object of ListIterator. The first next method call on this ListIterator object will return the element at the specified index passed to get the ListIterator object.

Iterators returned by these methods are fail-fast. That means if the list is modified after getting the Iterator by using some other means rather than Iterators own add or remove method, Iterator will throw ConcurrentModificationException.