Collection List Set SortedSet ArrayList LinkedList HashSet LinkedHashSet TreeSet的认识及用法

Posted on 2008-01-04 15:24 semovy 阅读(1425) 评论(0) 编辑收藏所属分类: JAVA基础

package com.semovy.test;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Comparator;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.ListIterator;
import java.util.SortedSet;
import java.util.TreeSet;

/**
*
* @author semovy@gmail.com
* Collection
* |        |
* List    Set______________________________________________
* |__________                      |       |               |
* |          |                     |       |               |
* ArrayList LinkedList        HashSet   LinkedHashSet     SortedSet
*                                                           |
*                                                           TreeSet
*/
public class CollectionTest {
/* Set容器中的对象是唯一的,所以加入Set容器的对象,必须重新equals()方法.作为唯一性的标识
* HashSet的排序规则是利用HashTable,所以HashSet容器的对象必须重新定义hashCode()方法
* 利用hashCode()方法,可以让快速找到容器中的对象,在比较两加入到容器中的对象是否相同时,会比较
* hashCode()方法返回是否相同,如果相同,则再利用equals()方法比较,如果两者都相同,则被看作相同的对象
* String 对象的hashCode(),equals已经被重新定义
*/
public static void main(String[] args)
{
  //String 对象的hashCode(),equals已经被重新定义
  //结果重复的内容对象被除去,并按按照hashCode()升序排序
  Collection<String> colStr = new HashSet<String>();
  colStr.add("ArrayList");
  colStr.add("LinkedList");
  colStr.add("HashSet");
  colStr.add("LinkedHashSet");
  colStr.add("LinkedSortedSet");
  colStr.add("ArrayList");
  CollectionTest ct = new CollectionTest();
  ct.display(colStr);
  //自定义类Employee.如果没有重新定义hashCode(),equals()方法,则不会除去重复内容的对象,不会自动按hashCode()排序
  Collection<Employee> colEmp = new HashSet<Employee>();
  colEmp.add(new Employee(1,"no.1","semovy","he is a hero."));
  colEmp.add(new Employee(2,"no.2","superman_wshm","from Shenzhen China"));
  colEmp.add(new Employee(3,"no.3","韦善茂","来自中国"));
  colEmp.add(new Employee(4,"no.4","joke","note1"));
  colEmp.add(new Employee(3,"no.3","韦善茂","来自中国"));
  ct.display(colEmp);
  //LinkedHashSet,既去除了内容重复的对象,又按时插入容器时的顺序,被迭代.
  Collection<Employee> linkedEmp = new LinkedHashSet<Employee>();
  linkedEmp.add(new Employee(1,"no.1","semovy","he is a hero."));
  linkedEmp.add(new Employee(2,"no.2","superman_wshm","from Shenzhen China"));
  linkedEmp.add(new Employee(3,"no.3","韦善茂","来自中国"));
  linkedEmp.add(new Employee(4,"no.4","joke","note1"));
  linkedEmp.add(new Employee(3,"no.3","韦善茂","来自中国"));
  ct.display(linkedEmp);
  //SortedSet接口,可以去除重复,并有比较器.
  SortedSet<String> ss = new TreeSet<String>();
  ss.add("1");
  ss.add("2");
  ss.add("3");
  ss.add("4");
  ss.add("4");
  ct.display(ss);

  //  SortedSet接口,可以去除重复,并有比较器.
  SortedSet<Employee> treeEmp = new TreeSet<Employee>(
    new Comparator<Employee>()//使用Employee泛型,匿名内部类比较器
    {

     public int compare(Employee arg0, Employee arg1) {

      return arg1.getName().compareTo(arg0.getName());//按照名称比较降序排序
     }

    }
    );
  treeEmp.add(new Employee(1,"no.1","semovy","he is a hero."));
  treeEmp.add(new Employee(2,"no.2","superman_wshm","from Shenzhen China"));
  treeEmp.add(new Employee(3,"no.3","韦善茂","来自中国"));
  treeEmp.add(new Employee(4,"no.4","joke","note1"));
  treeEmp.add(new Employee(3,"no.3","韦善茂","来自中国"));
  ct.display(treeEmp);

  //SortedSet接口,可以去除重复,并有比较器.比较器名为comparatorById
  ComparatorById comparatorById = new ComparatorById();
  SortedSet<Employee> treeEmp1 = new TreeSet<Employee>(comparatorById);
  treeEmp1.add(new Employee(1,"no.1","semovy","he is a hero."));
  treeEmp1.add(new Employee(2,"no.2","superman_wshm","from Shenzhen China"));
  treeEmp1.add(new Employee(3,"no.3","韦善茂","来自中国"));
  treeEmp1.add(new Employee(4,"no.4","joke","note1"));
  treeEmp1.add(new Employee(3,"no.3","韦善茂","来自中国"));
  ct.display(treeEmp1);

  System.out.println();
  System.out.println(treeEmp1.last().toString());
  System.out.println(treeEmp1.first().toString());

  //用List接口的实现
  //ArrayList.基于数组的实现,添加与删除的效率慢于LinkedList,
  //LinkedList基于双向链表的实现 ,添加与删除的效率快于ArrayList,但迭代遍历的效率不如ArrayList
  List<Employee> empList = new ArrayList<Employee>();
  empList.add(new Employee(1,"no.1","semovy","he is a hero."));
  empList.add(new Employee(2,"no.2","superman_wshm","from Shenzhen China"));
  empList.add(new Employee(3,"no.3","韦善茂","来自中国"));
  empList.add(new Employee(4,"no.4","joke","note1"));
  empList.add(new Employee(3,"no.3","韦善茂","来自中国"));
  ct.display(empList);

  Employee[] arrEmp = empList.toArray(new Employee[0]);
  Arrays.sort(arrEmp, comparatorById);//用Arrays.sort静态方法排序,比较器是comparatorById

  ct.display(arrEmp);

  LinkedList<Employee> linkedListEmp = new LinkedList<Employee>();
  linkedListEmp.add(new Employee(1,"no.1","semovy","he is a hero."));
  linkedListEmp.add(new Employee(2,"no.2","superman_wshm","from Shenzhen China"));
  linkedListEmp.add(new Employee(3,"no.3","韦善茂","来自中国"));
  linkedListEmp.add(new Employee(4,"no.4","joke","note1"));
  linkedListEmp.add(new Employee(3,"no.3","韦善茂","来自中国"));
  ct.display(linkedListEmp);

  ListIterator<Employee> ll = linkedListEmp.listIterator();
  while(ll.hasNext())
  {
   Employee em = ll.next();
   System.out.println("index:" + ll.nextIndex());
   if(em.getId() == 3)
    ll.remove();//删除刚跨过的元素
  }
  ct.display(linkedListEmp);
}

/**
* display all the objects in Collection
* @prama Conllection
*/
public void display(Collection c)//用for循环集合
{
  System.out.println();
  for(Object obj : c)
   System.out.println(obj.toString() + " ");
}
public void display(Object[] arr)//用for循环数组
{
  System.out.println();
  for(Object obj : arr)
   System.out.println(obj.toString() + " ");
}
}
/**
* 比较器接口Comparator 按id.升序
*/
class ComparatorById implements Comparator<Employee>
{
public int compare(Employee e1 ,Employee e2)
{
  return e1.getId() - e2.getId();//按照id比较升序排序
}
}

//==============================================================================
结果:

ArrayList
HashSet
LinkedSortedSet
LinkedHashSet
LinkedList

[ ID: 3 , No.: no.3 , Name: 韦善茂 , Note: 来自中国 ]
[ ID: 2 , No.: no.2 , Name: superman_wshm , Note: from Shenzhen China ]
[ ID: 1 , No.: no.1 , Name: semovy , Note: he is a hero. ]
[ ID: 4 , No.: no.4 , Name: joke , Note: note1 ]

[ ID: 1 , No.: no.1 , Name: semovy , Note: he is a hero. ]
[ ID: 2 , No.: no.2 , Name: superman_wshm , Note: from Shenzhen China ]
[ ID: 3 , No.: no.3 , Name: 韦善茂 , Note: 来自中国 ]
[ ID: 4 , No.: no.4 , Name: joke , Note: note1 ]

1
2
3
4

[ ID: 4 , No.: no.4 , Name: joke , Note: note1 ]
[ ID: 1 , No.: no.1 , Name: semovy , Note: he is a hero. ]

[ ID: 1 , No.: no.1 , Name: semovy , Note: he is a hero. ]
[ ID: 2 , No.: no.2 , Name: superman_wshm , Note: from Shenzhen China ]
[ ID: 3 , No.: no.3 , Name: 韦善茂 , Note: 来自中国 ]
[ ID: 3 , No.: no.3 , Name: 韦善茂 , Note: 来自中国 ]
[ ID: 4 , No.: no.4 , Name: joke , Note: note1 ]

[ ID: 1 , No.: no.1 , Name: semovy , Note: he is a hero. ]
[ ID: 2 , No.: no.2 , Name: superman_wshm , Note: from Shenzhen China ]
[ ID: 4 , No.: no.4 , Name: joke , Note: note1 ]

新用户注册刷新评论列表


只有注册用户登录后才能发表评论。




网站导航: 博客园 IT新闻知识库 C++博客博问管理
相关文章: Java提供的剪贴板[转] 省空间去保存这个字符串 URLEncoder.encode(str,"编码") new URLDecoder().decode(str,"编码") Java连接池 ThreadLocal使用 JAVA进制转换数组 Collection List Set Map的比较 List、Set、数组之间的转换 Log4j简介 java中文件操作大全

semovy

Collection List Set SortedSet ArrayList LinkedList HashSet LinkedHashSet TreeSet的认识及用法

日历

留言簿(7)

随笔分类

随笔档案(1)

文章分类(377)

文章档案(356)

相册

收藏夹(18)

昨天重现

搜索

最新评论