HashMap和LinkedHashMap都是实现Map接口，区别在于HashMap并不是按插入次序顺序存放的，而LinkedHashMap是顺序存放的

public static void  main(String[] args) {        
Map<String,String> hashmap = new HashMap<String,String>();   

Map<String,String> linkmap  = new LinkedHashMap<String,String>();    

for(int i=0;i<10;i++){      
hashmap.put(""+i, ""+i);     
linkmap.put(""+i, ""+i);    }    
System.out.println("HashMap遍历输出：");    

for(Entry<String,String> entry:hashmap.entrySet()){      
System.out.print(entry.getKey()+" ");    
}    

System.out.println("");    
System.out.println("LinkedHashMap遍历输出：");    
for(Entry<String,String> entry:linkmap.entrySet()){      
System.out.print(entry.getKey()+" "
);   
 }  
}

HashMap遍历输出：3 2 1 0 7 6 5 4 9 8
LinkedHashMap遍历输出：0 1 2 3 4 5 6 7 8 9