总结

Java容器实际上只有三种:Map , List, Set;但每种接口都有不同的实现版本.它们的区别可以归纳为由什么在背后支持它们.也就是说,你使用的接口是由什么样的数据结构实现的.

List的选择:

比如:ArrayList（读快改慢）和LinkedList（改快读慢）都实现了List接口.因此无论选择哪一个,基本操作都一样.但ArrayList是由数组提供底层支持.而LinkedList是由双向链表实现的.所以,如果要经常向List里插入或删除数据,LinkedList会比较好.否则应该用速度更快的ArrayList。

Set的选择

HashSet总是比TreeSet 性能要好.而后者存在的理由就是它可以维持元素的排序状态.所以,如果需要一个排好序的Set时,才应该用TreeSet。

Map选择:

同上,尽量选择HashMap。

（http://blog.csdn.net/dandanzmc/article/details/23447827）

容器类对象在调用remove,contains等方法时需要比较对象是否相等，这会涉及到对象类型的equals方法和hashCode方法；对于自定义的类型，需要要重写equals 和 hashCode方法以及实现自定义的对象相等规则。

import java.util.*;//包含Collection接口/*范例名称： * 原文件名称： * 要点： * 1. Collection基本结构图 * 2. Collections类 * 3. For、Generic、Auto-boxing / unboxing (循环、泛型、自动打包/解包) * 4. 六个接口: Collection、Set、List、Map、Iterator、Comparable */public class CollectionTest {	public static void main(String[] args){		Collection c=new ArrayList();		//放入不容类型的对象		c.add("hello");//添加元素（增）		c.add(new Name("f11","11"));		c.add(new Integer(100));		System.out.println(c);				Collection c2=new HashSet();		c2.add("hello");		c2.add(new Name2("f11","11"));		c2.add(new Integer(100));		c2.remove("hello");         c2.remove(new Integer(100));        System.out.println(c2.remove(new Name2("f11","11")));        System.out.println(c2);                //迭代器Iterator遍历（查）        Collection c3=new HashSet();//无序        c3.add(new Name2("ffff1","11"));        c3.add(new Name2("f2", "12"));        c3.add(new Name2("fff3", "13"));        Iterator i=c3.iterator();        while(i.hasNext()){        	//next()的返回值是Object类型，需要强制类型转换        	Name2 n=(Name2)i.next();        	System.out.print(n.getFirstName()+" ");        }        System.out.println("");        //删除元素（删）        for(Iterator i2=c3.iterator();i2.hasNext();){        	Name2 name=(Name2)i2.next();        	if(name.getFirstName().length()<5){        		i2.remove();//不能换成c3.remove(name2);        	}        }        System.out.println(c3);                //List实例        List list1=new LinkedList();        for(int j=0;j<9;j++){list1.add("Hello"+j);}        Collections.shuffle(list1);//Collections类；随机排列list对象元素        System.out.println(list1);        Collections.sort(list1);//排序        System.out.println(list1);        Collections.reverse(list1);//逆序        System.out.println(list1);                //对Name3类进行排序        List list2=new LinkedList();        list2.add(new Name3("China", "ch"));        list2.add(new Name3("Japan", "jp"));        list2.add(new Name3("Singapore", "sg"));        list2.add(new Name3("Hongkong", "hk"));        System.out.println(list2);        Collections.sort(list2);//Sorts the specified list into ascending order, according to the natural ordering of its elements. All elements in the list must implement the Comparable interface.        System.out.println(list2);                //Map实例        Map m1=new HashMap();        Map m2=new TreeMap();        m1.put("one", new Integer(1));//1.5版本以前；之后可以用m1.put("one",1)代替，自动打包功能        m1.put("two", new Integer(3));        m2.put("A",new Integer(1));        m2.put("B", new Integer(2));        if(m1.containsKey("two")){        	int k=((Integer)m1.get("two")).intValue();        	System.out.println(k);        }        Map m3=new HashMap(m1);        m3.putAll(m2);        System.out.println(m3);                //Map实例_泛型        Map
    
      m11=new HashMap
     
      ();        Map
      
        m12=new HashMap
       
        ();        m11.put("one", 1);        m11.put("two", 3);        m12.put("A", 1);        m12.put("B", 2);        if(m11.containsKey("two")){        	int m=m11.get("two");//Integer自动解包为int        	System.out.println(m);        }        Map
        
          m13=new HashMap
         
          (m11); m13.putAll(m12); System.out.println(m13); //检测String数组中相同字符串的数目 String[] testString=new String[5]; testString[0]="aa";testString[1]="bb";testString[2]="cc";testString[3]="bb";testString[4]="aa"; Map
          
            mTest=new HashMap
           
            (); for(int ii=0;ii
            
              list3=new LinkedList
             
              (); list3.add(new Name4("China", "ch")); list3.add(new Name4("Japan", "jp")); list3.add(new Name4("Singapore", "sg")); list3.add(new Name4("Hongkong", "hk")); System.out.println(list3); Collections.sort(list3);//Sorts the specified list into ascending order, according to the natural ordering of its elements. All elements in the list must implement the Comparable interface. System.out.println(list3); }}class Name{ private String firstName,lastName; public Name(String firstName,String lastName){ this.firstName=firstName;this.lastName=lastName; } public String getFirstName(){return firstName;} public String getLastName(){return lastName;} public String toString(){return firstName+" "+lastName;}//重写了toString方法 }class Name2{ private String firstName,lastName; public Name2(String firstName,String lastName){ this.firstName=firstName;this.lastName=lastName; } public String getFirstName(){return firstName;} public String getLastName(){return lastName;} public String toString(){return firstName+" "+lastName;}//重写了toString方法 //重写equals跟hashCode方法 public boolean equals(Object obj){ if(obj instanceof Name2){ Name2 name=(Name2)obj; return (firstName.equals(name.firstName) && lastName.equals(name.lastName)); } return super.equals(obj); } public int hashCode(){ return firstName.hashCode(); }}//Comparable接口class Name3 implements Comparable { private String firstName,lastName; public Name3(String firstName,String lastName){ this.firstName=firstName;this.lastName=lastName; } public String getFirstName(){return firstName;} public String getLastName(){return lastName;} public String toString(){return firstName+" "+lastName;}//重写了toString方法 //重写equals跟hashCode方法 public boolean equals(Object obj){ if(obj instanceof Name3){ Name3 name=(Name3)obj; return (firstName.equals(name.firstName) && lastName.equals(name.lastName)); } return super.equals(obj); } public int hashCode(){ return firstName.hashCode(); } //重写compareTo方法 public int compareTo(Object o){ Name3 n=(Name3)o; int lastCmp=lastName.compareTo(n.lastName); return (lastCmp!=0?lastCmp:firstName.compareTo(n.firstName)); }}//Comparable接口_泛型写法class Name4 implements Comparable
              
                { private String firstName,lastName; public Name4(String firstName,String lastName){ this.firstName=firstName;this.lastName=lastName; } public String getFirstName(){return firstName;} public String getLastName(){return lastName;} public String toString(){return firstName+" "+lastName;}//重写了toString方法 //重写equals跟hashCode方法 public boolean equals(Name4 name){ return (firstName.equals(name.firstName) && lastName.equals(name.lastName)); } public int hashCode(){ return firstName.hashCode(); } //重写compareTo方法 public int compareTo(Name4 o){ int lastCmp=lastName.compareTo(o.lastName); return (lastCmp!=0?lastCmp:firstName.compareTo(o.firstName)); }}

输出结果：

[hello, f11 11, 100]true[]fff3 ffff1 f2 [ffff1 11][Hello4, Hello2, Hello3, Hello0, Hello7, Hello6, Hello8, Hello1, Hello5][Hello0, Hello1, Hello2, Hello3, Hello4, Hello5, Hello6, Hello7, Hello8][Hello8, Hello7, Hello6, Hello5, Hello4, Hello3, Hello2, Hello1, Hello0][China ch, Japan jp, Singapore sg, Hongkong hk][China ch, Hongkong hk, Japan jp, Singapore sg]3{A=1, B=2, two=3, one=1}3{A=1, B=2, two=3, one=1}3 distinct words detected:{aa=2, bb=2, cc=1}[China ch, Japan jp, Singapore sg, Hongkong hk][China ch, Hongkong hk, Japan jp, Singapore sg]

这一章其实是训练数据结构的好地方，可以自己实现一下基本数据结构的源码（ArrayList、LinkedList、Stack、Queue、Tree等）