Home Java javaTutorial Detailed explanation of instance methods of vector class

Detailed explanation of instance methods of vector class

May 06, 2017 pm 01:26 PM

This article mainly introduces the detailed explanation of the use of Java vector class and related information of examples. Friends in need can refer to the following

Basic operation examples

VectorApp.java

import java.util.Vector; 
import java.lang.*; 
import java.util.Enumeration; 
public class VectorApp 
{ 
 public static void main(String args[]) 
 { 
 Vector v1 = new Vector(); 
 Integer integer1= new Integer(1); 
 //加入为字符串对象 
 v1.addElement("one"); 
 //加入的为integer的对象 
 v1.addElement(integer1); 
 v1.addElement(integer1); 
 v1.addElement("two"); 
 v1.addElement(new Integer(2)); 
 v1.addElement(integer1); 
 v1.addElement(integer1); 
 //转为字符串并打印 
 System.out.println("The Vector v1 is:\n\t"+v1); 
 //向指定位置插入新对象 
 v1.insertElement("three",2); 
 v1.insertElement(new Float(3.9),3); 
 System.out.println("The Vector v1(used method 
 insertElementAt()is:\n\t)"+v1); 
 //将指定位置的对象设置为新的对象 
 //指定位置后的对象依次往后顺延 
 v1.setElementAt("four",2); 
 System.out.println("The vector v1 cused method setElmentAt()is:\n\t"+v1); 
 v1.removeElement(integer1); 
 //从向量对象v1中删除对象integer1 
 //由于存在多个integer1,所以从头开始。 
 //找删除找到的第一个integer1. 
 Enumeration enum = v1.elements(); 
 System.out.println("The vector v1 (used method removeElememt()is"); 
 while(enum.hasMoreElements()) 
 System.out.println(enum.nextElement()+""); 
 System.out.println(); 
 //使用枚举类(Enumeration)的方法取得向量对象的每个元素。 
 System.out.println("The position of Object1(top-to-botton):"+v1.indexOf(integer1)); 
 System.out.println("The position of Object1(tottom-to-top):"+v1.lastIndexOf(integer1)); 
 //按不同的方向查找对象integer1所处的位置 
 v1.setSize(4); 
 System.out.println("The new Vector(resized the vector)is:"+v1); 
 //重新设置v1的大小,多余的元素被抛弃 
 } 
}
Copy after login

Run result:

E:\java01>java VectorApp 
The vector v1 is:[one,1,1,two,2,1,1] 
The vector v1(used method insetElementAt()) is: 
[one,1,three,3.9,1,two,2,1,1] 
The vector v1(used method setElementAt()) is: 
[one,1,four,3.9,1,two,2,1,1] 
The vector v1(useed method removeElement()) is: 
one four 3.9 1 two 2 1 1 
The position of object1(top-to-botton):3 
The position of object1(botton-to-top):7 
The new Vector(resized the vector) is: 
[one,four,3.9,1]
Copy after login

1x expansion of Vertor

Do you still remember that ArrayList expands to 0.5 times the size of array each time? Vector is slightly different from ArrayList when performing expansion operations

protected int capacityIncrement;//用于指定每次扩容的容量
private void grow(int minCapacity) {
 // overflow-conscious code
 int oldCapacity = elementData.length;
 int newCapacity = oldCapacity + ((capacityIncrement > 0) ?
   capacityIncrement : oldCapacity);//如不指定capacityIncrement,默认扩容的容量为原数组的容量
 if (newCapacity - minCapacity < 0)
 newCapacity = minCapacity;
 if (newCapacity - MAX_ARRAY_SIZE > 0)
 newCapacity = hugeCapacity(minCapacity);
 elementData = Arrays.copyOf(elementData, newCapacity);
}
Copy after login

Careful friends can find that there is an additional capacityIncrement

variable in Vector, which is used to specify the increment of each expansion. If you do not specify this variable, you can find in grow that the Vector is expanded to 1 times the size of the original array by default

ThreadSafety

Vertor is thread-safe!

Another conspicuous thing in the Vertor source code is that most methods have the synchronized keyword. Everyone knows that this keyword is used for thread synchronization, so the Vector class is a thread safe!


But even if all its methods are modified to be synchronized, it does not mean that synchronization will never be needed when calling it:

private static Vector<Integer> vector=new Vector<Integer>();
public static void main(String[] args) { 
 while(true)
 {
 for(int i=0;i<10;i++)
 {
 vector.add(i);
 }
 Thread removeThread=new Thread(new Runnable(){
 @Override
 public void run()
 {
 for(int i=0;i<vector.size();i++)
 {
 vector.remove(i);
 }
 }
 });
 Thread printThread=new Thread(new Runnable(){
 @Override
 public void run()
 {
 for(int i=0;i<vector.size();i++)
 {
 System.out.println(vector.get(i));
 }
 }
 }); 
 removeThread.start();
 printThread.start();
 while(Thread.activeCount()>20); 
 }
}
Copy after login
When everyone runs this code After running for a short period of time, you will find an

ArrayIndexOutOfBoundsException exception. Here, the Vector's get, remove, size methods are synchronized modified, but in a multi-threaded environment , if no additional synchronization measures are taken on the method side, this code is still unsafe. If one thread deletes the element with serial number i, and another thread accesses this i, it will directly throw an exception back, so this code is guaranteed to Security needs to be modified by adding synchronized inside run.

【Related Recommendations】

1.

Java Free Video Tutorial

2.

Java Basic Introduction Video Tutorial

3.

FastJson Development Tutorial

The above is the detailed content of Detailed explanation of instance methods of vector class. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
2 weeks ago By 尊渡假赌尊渡假赌尊渡假赌
Repo: How To Revive Teammates
1 months ago By 尊渡假赌尊渡假赌尊渡假赌
Hello Kitty Island Adventure: How To Get Giant Seeds
4 weeks ago By 尊渡假赌尊渡假赌尊渡假赌

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

Square Root in Java Square Root in Java Aug 30, 2024 pm 04:26 PM

Guide to Square Root in Java. Here we discuss how Square Root works in Java with example and its code implementation respectively.

Perfect Number in Java Perfect Number in Java Aug 30, 2024 pm 04:28 PM

Guide to Perfect Number in Java. Here we discuss the Definition, How to check Perfect number in Java?, examples with code implementation.

Random Number Generator in Java Random Number Generator in Java Aug 30, 2024 pm 04:27 PM

Guide to Random Number Generator in Java. Here we discuss Functions in Java with examples and two different Generators with ther examples.

Weka in Java Weka in Java Aug 30, 2024 pm 04:28 PM

Guide to Weka in Java. Here we discuss the Introduction, how to use weka java, the type of platform, and advantages with examples.

Armstrong Number in Java Armstrong Number in Java Aug 30, 2024 pm 04:26 PM

Guide to the Armstrong Number in Java. Here we discuss an introduction to Armstrong's number in java along with some of the code.

Smith Number in Java Smith Number in Java Aug 30, 2024 pm 04:28 PM

Guide to Smith Number in Java. Here we discuss the Definition, How to check smith number in Java? example with code implementation.

Java Spring Interview Questions Java Spring Interview Questions Aug 30, 2024 pm 04:29 PM

In this article, we have kept the most asked Java Spring Interview Questions with their detailed answers. So that you can crack the interview.

Break or return from Java 8 stream forEach? Break or return from Java 8 stream forEach? Feb 07, 2025 pm 12:09 PM

Java 8 introduces the Stream API, providing a powerful and expressive way to process data collections. However, a common question when using Stream is: How to break or return from a forEach operation? Traditional loops allow for early interruption or return, but Stream's forEach method does not directly support this method. This article will explain the reasons and explore alternative methods for implementing premature termination in Stream processing systems. Further reading: Java Stream API improvements Understand Stream forEach The forEach method is a terminal operation that performs one operation on each element in the Stream. Its design intention is

See all articles