hasSet,TreeSet,ArrayList,LinkedList,Vector,HashMap,HashTable,TreeMap利用Iterator进行输出

基础类，没有重写hashCode()和equals()方法：

package niukewang;

import java.util.Objects;

public class setClass {

    String a;
    String b;
    public setClass(String a, String b)
    {
        this.a=a;
        this.b=b;    
    }
    
}

测试类：

package niukewang;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.TreeMap;
import java.util.TreeSet;
import java.util.Vector;


public class test1 {

    public static void main(String args[]) 
    { 
        setClass s1=new setClass("http://www.yjbys.com/", "");
        setClass s2=new setClass("http://www.yjbys.com1/", "");
        setClass s3=new setClass("http://www.yjbys.com2/", "");
        setClass s4=new setClass("http://www.yjbys.com2/", "");
        
        //hasSet
        System.out.println("hasSet......");
        Set<setClass> set=new HashSet<setClass>();
        set.add(s1);
        set.add(s2);
        set.add(s3);
        set.add(s4);
        Iterator it= set.iterator();
        while(it.hasNext())
        {
            setClass ob=(setClass)it.next();
            System.out.println(ob.a);
        }
        
/*        //TreeSet
        System.out.println("\nTreeSet........");
        Set<setClass> tree=new TreeSet<setClass>();
        tree.add(s1);
        tree.add(s2);
        tree.add(s3);
        tree.add(s4);
        Iterator treeit=tree.iterator();
        while(treeit.hasNext())
        {
            setClass ob=(setClass) treeit.next();
            System.out.println(ob.a);
        }
        */
        //TreeMap
/*        System.out.println("\nTreeMap.........");
        Map<setClass,String> treemap=new TreeMap<setClass,String>();
        treemap.put(s1, "TreeMap one");
        treemap.put(s2, "TreeMap two");
        treemap.put(s3, "TreeMap three");
        treemap.put(s4, "TreeMap four");
        for(Map.Entry<setClass, String> entry: treemap.entrySet())
        {
            System.out.println("The treemap key is "+entry.getKey().a+" The value is "+ entry.getValue());
        }*/
        
        //HasMap
        System.out.println("\nHashMap......");
        Map<setClass,String> hashmap=new HashMap<setClass, String>();
        hashmap.put(s1, "HashMap one");
        hashmap.put(s2, "HashMap two");
        hashmap.put(s3, "HashMap three");
        hashmap.put(s4, "HashMap four");
        for(Map.Entry<setClass, String> entry : hashmap.entrySet())
        {
            System.out.println("The key is "+entry.getKey().a+" The value is "+entry.getValue());
        }
        
        //HasTable
        System.out.println("\nHashTable......");
        Map<setClass,String> hashtable=new Hashtable<setClass, String>();
        hashtable.put(s1, "HashTable one");
        hashtable.put(s2, "HashTable two");
        hashtable.put(s3, "HashTable three");
        hashtable.put(s4, "HashTable four");
        for(Map.Entry<setClass, String> entry: hashtable.entrySet())
        {
            System.out.println("The HashTable key is "+entry.getKey().a+" The HashTable value is "+entry.getValue());
        }
        
        //LinkedList
        System.out.println("\nLinkedList.....");
        List list=new LinkedList();
        list.add(s1);
        list.add(s2);
        list.add(s3);
        list.add(s4);
        Iterator listit=list.iterator();
        while(listit.hasNext())
        {
            setClass ob=(setClass)listit.next();
            System.out.println(ob.a);
        }

        //ArrayList
        System.out.println("\nArrayList.....");
        List array=new ArrayList();
        array.add(s1);
        array.add(s2);
        array.add(s3);
        array.add(s4);
        Iterator arrayit=array.iterator();
        while(arrayit.hasNext())
        {
            setClass ob=(setClass)arrayit.next();
            System.out.println(ob.a);
        }
        
        //vector
        System.out.println("\nvector.....");
        Vector v=new Vector();
        v.add(s1);
        v.add(s2);
        v.add(s3);
        v.add(s4);
        Iterator vit=v.iterator();
        while(vit.hasNext())
        {
            setClass  ob=(setClass)vit.next();
            System.out.println(ob.a);
        }
            
    }
}

输出结果：
由于没有重写hasCode和equals方法，所以s3和s4对象认为是不相同的，因此在set中被看成了不同的对象；同理，在hashMap和hashTable中，其根据hashCode的值对数据进行存储的，所以，hashcode的值不一样，因此也存储了4个数。

hasSet......
http://www.yjbys.com1/
http://www.yjbys.com2/
http://www.yjbys.com/
http://www.yjbys.com2/

HashMap......
The key is http://www.yjbys.com1/ The value is HashMap two
The key is http://www.yjbys.com2/ The value is HashMap four
The key is http://www.yjbys.com/ The value is HashMap one
The key is http://www.yjbys.com2/ The value is HashMap three

HashTable......
The HashTable key is http://www.yjbys.com2/ The HashTable value is HashTable four
The HashTable key is http://www.yjbys.com2/ The HashTable value is HashTable three
The HashTable key is http://www.yjbys.com1/ The HashTable value is HashTable two
The HashTable key is http://www.yjbys.com/ The HashTable value is HashTable one

LinkedList.....
http://www.yjbys.com/
http://www.yjbys.com1/
http://www.yjbys.com2/
http://www.yjbys.com2/

ArrayList.....
http://www.yjbys.com/
http://www.yjbys.com1/
http://www.yjbys.com2/
http://www.yjbys.com2/

vector.....
http://www.yjbys.com/
http://www.yjbys.com1/
http://www.yjbys.com2/
http://www.yjbys.com2/

改变之后的。

基础类：

package niukewang;

import java.util.Objects;

public class setClass {

    String a;
    String b;
    public setClass(String a, String b)
    {
        this.a=a;
        this.b=b;    
    }
    
    public int hashCode() {
        return a.hashCode();
    }
    
    public boolean equals(Object obj)
    {
        if(obj==null) return false;
        
        if(getClass() != obj.getClass()) return false;
        
        final setClass s=(setClass)obj;
        
        return Objects.equals(this.a, s.a);
    }
}

测试类：

package niukewang;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.TreeMap;
import java.util.TreeSet;
import java.util.Vector;


public class test1 {

    public static void main(String args[]) 
    { 
        setClass s1=new setClass("http://www.yjbys.com/", "");
        setClass s2=new setClass("http://www.yjbys.com1/", "");
        setClass s3=new setClass("http://www.yjbys.com2/", "");
        setClass s4=new setClass("http://www.yjbys.com2/", "");
        
        //hasSet
        System.out.println("hasSet......");
        Set<setClass> set=new HashSet<setClass>();
        set.add(s1);
        set.add(s2);
        set.add(s3);
        set.add(s4);
        Iterator it= set.iterator();
        while(it.hasNext())
        {
            setClass ob=(setClass)it.next();
            System.out.println(ob.a);
        }
        
/*        //TreeSet
        System.out.println("\nTreeSet........");
        Set<setClass> tree=new TreeSet<setClass>();
        tree.add(s1);
        tree.add(s2);
        tree.add(s3);
        tree.add(s4);
        Iterator treeit=tree.iterator();
        while(treeit.hasNext())
        {
            setClass ob=(setClass) treeit.next();
            System.out.println(ob.a);
        }
        */
        //TreeMap
/*        System.out.println("\nTreeMap.........");
        Map<setClass,String> treemap=new TreeMap<setClass,String>();
        treemap.put(s1, "TreeMap one");
        treemap.put(s2, "TreeMap two");
        treemap.put(s3, "TreeMap three");
        treemap.put(s4, "TreeMap four");
        for(Map.Entry<setClass, String> entry: treemap.entrySet())
        {
            System.out.println("The treemap key is "+entry.getKey().a+" The value is "+ entry.getValue());
        }*/
        
        //HasMap
        System.out.println("\nHashMap......");
        Map<setClass,String> hashmap=new HashMap<setClass, String>();
        hashmap.put(s1, "HashMap one");
        hashmap.put(s2, "HashMap two");
        hashmap.put(s3, "HashMap three");
        hashmap.put(s4, "HashMap four");
        for(Map.Entry<setClass, String> entry : hashmap.entrySet())
        {
            System.out.println("The key is "+entry.getKey().a+" The value is "+entry.getValue());
        }
        
        //HasTable
        System.out.println("\nHashTable......");
        Map<setClass,String> hashtable=new Hashtable<setClass, String>();
        hashtable.put(s1, "HashTable one");
        hashtable.put(s2, "HashTable two");
        hashtable.put(s3, "HashTable three");
        hashtable.put(s4, "HashTable four");
        for(Map.Entry<setClass, String> entry: hashtable.entrySet())
        {
            System.out.println("The HashTable key is "+entry.getKey().a+" The HashTable value is "+entry.getValue());
        }
        
        //LinkedList
        System.out.println("\nLinkedList.....");
        List list=new LinkedList();
        list.add(s1);
        list.add(s2);
        list.add(s3);
        list.add(s4);
        Iterator listit=list.iterator();
        while(listit.hasNext())
        {
            setClass ob=(setClass)listit.next();
            System.out.println(ob.a);
        }

        //ArrayList
        System.out.println("\nArrayList.....");
        List array=new ArrayList();
        array.add(s1);
        array.add(s2);
        array.add(s3);
        array.add(s4);
        Iterator arrayit=array.iterator();
        while(arrayit.hasNext())
        {
            setClass ob=(setClass)arrayit.next();
            System.out.println(ob.a);
        }
        
        //vector
        System.out.println("\nvector.....");
        Vector v=new Vector();
        v.add(s1);
        v.add(s2);
        v.add(s3);
        v.add(s4);
        Iterator vit=v.iterator();
        while(vit.hasNext())
        {
            setClass  ob=(setClass)vit.next();
            System.out.println(ob.a);
        }
            
    }
}

输出结果：

由于覆盖了hashCode和equals方法，因此s3和s4被认为是相同的对象。

hasSet......
http://www.yjbys.com1/
http://www.yjbys.com/
http://www.yjbys.com2/

HashMap......
The key is http://www.yjbys.com1/ The value is HashMap two
The key is http://www.yjbys.com/ The value is HashMap one
The key is http://www.yjbys.com2/ The value is HashMap four

HashTable......
The HashTable key is http://www.yjbys.com1/ The HashTable value is HashTable two
The HashTable key is http://www.yjbys.com/ The HashTable value is HashTable one
The HashTable key is http://www.yjbys.com2/ The HashTable value is HashTable four

LinkedList.....
http://www.yjbys.com/
http://www.yjbys.com1/
http://www.yjbys.com2/
http://www.yjbys.com2/

ArrayList.....
http://www.yjbys.com/
http://www.yjbys.com1/
http://www.yjbys.com2/
http://www.yjbys.com2/

vector.....
http://www.yjbys.com/
http://www.yjbys.com1/
http://www.yjbys.com2/
http://www.yjbys.com2/

但是TreeSet和TreeMap还是不能这么输出，因为要实现Comparable接口。因为TreesSet和TreeMap是一个有序的集合，必须知道你想怎么排列。你可以换成LinkedList或ArrayList就不用了。

下一篇文章是对TreeSet和TreeMap的输出。

 

来源：https://www.cnblogs.com/Berryxiong/p/6138314.html