Java Vector类

Vector实现了一个动态数组。它类似于ArrayList，但有两个区别：

• Vector是同步的。

• Vector包含许多不属于集合框架的遗留方法。

如果您不事先知道数组的大小，或者只需要在程序的生命周期中更改大小的数组，那么Vector就会非常有用。

以下是Vector类提供的构造函数列表。

除了从其父类继承的方法之外，Vector 还定义了以下方法 −

示例

以下程序说明了该集合支持的几种方法：

import java.util.*;
public class VectorDemo {

   public static void main(String args[]) {
      // initial size is 3, increment is 2
      Vector v = new Vector(3, 2);
      System.out.println("Initial size: " + v.size());
      System.out.println("Initial capacity: " + v.capacity());

      v.addElement(new Integer(1));
      v.addElement(new Integer(2));
      v.addElement(new Integer(3));
      v.addElement(new Integer(4));
      System.out.println("Capacity after four additions: " + v.capacity());

      v.addElement(new Double(5.45));
      System.out.println("Current capacity: " + v.capacity());

      v.addElement(new Double(6.08));
      v.addElement(new Integer(7));
      System.out.println("Current capacity: " + v.capacity());

      v.addElement(new Float(9.4));
      v.addElement(new Integer(10));
      System.out.println("Current capacity: " + v.capacity());

      v.addElement(new Integer(11));
      v.addElement(new Integer(12));
      System.out.println("First element: " + (Integer)v.firstElement());
      System.out.println("Last element: " + (Integer)v.lastElement());

      if(v.contains(new Integer(3)))
         System.out.println("Vector contains 3.");

      // enumerate the elements in the vector.
      Enumeration vEnum = v.elements();
      System.out.println("\nElements in vector:");

      while(vEnum.hasMoreElements())
         System.out.print(vEnum.nextElement() + " ");
      System.out.println();
   }
}

这将产生以下结果 –

输出

Initial size: 0
Initial capacity: 3
Capacity after four additions: 5
Current capacity: 5
Current capacity: 7
Current capacity: 9
First element: 1
Last element: 12
Vector contains 3.

Elements in vector:
1 2 3 4 5.45 6.08 7 9.4 10 11 12