21. Vector constructors in collection framework and capacity and ensureCapacity method in vector
Vector constructors capacity and ensureCapacity method in vector in collection framework
there are four types of constructor available in vector
Vector(),
Vector(Collection c),
Vector(int initialCapacity),
Vector(int initialCapacity, int capacityIncrement),
properties of vector:
Underlined data structure is Resizable/ Growable array
Duplicates are allowed
Insertion order is preserved
Null insertion is allowed
Homogeneous/ Heterogeneous elements are allowed
Vector implements RandomAccess, clonable and serializable interface
Most of the method in vector are synchronised hence thread safe.
Best choice – whenever frequent operation is retrieval
Worst choice – whenever frequent operation is insertion or deletion
Demo program :
package com.techiedeveloper.list;
import java.util.Vector;
public class VectorDemo {
public static void main(String[] args) {
Vector<Integer> defaultVector = new Vector<>();//first constructor
defaultVector.ensureCapacity(25);
System.out.println("default capacity"+defaultVector.capacity());//25
for(int i=0;i<25;i++) {
defaultVector.add(i);
}
defaultVector.add(11);
System.out.println(defaultVector);//[0,1,2,3,4,5,6,,,,,,,,,24,11]total 26 element
System.out.println("current capacity"+defaultVector.capacity());//50
Vector<Integer> collVector = new Vector<>(defaultVector);//second constructor
System.out.println("collVector"+collVector);//[0,1,2,3,4,5,6,,,,,,,,,24,11]total 26 element
Vector<Integer> initCapVector = new Vector<>(25,2);//here initial capacity is 25 and incremental capacity is 2
System.out.println("inintcapvector capacity"+initCapVector.capacity());//25
for(int i=0;i<25;i++) {
initCapVector.add(i);
}
System.out.println(initCapVector.capacity());//25
initCapVector.add(26);
System.out.println("new cap"+initCapVector.capacity());//27
}
}