1.把Map中的Key或Value转化为数组
HashMap ssMap = new HashMap();
Counter counters[] = new Counter[ssMap.size()];
ssMap.values().toArray(counters); //转化，counters不需实例化
Arrays.sort(counters,new DfComparator());//排序
2. Comparator 实例
继承Comparator也可以实现排序，但相对Comparable接口更加灵活，用不同的Comparator实例可以实现不同的排序方法
class DfComparator implements Comparator
{
public int compare(Object o1, Object o2) {
// TODO Auto-generated method stub
Counter c1 = (Counter)o1;
Counter c2 = (Counter)o2;
return c2.df – c1.df;
}
public boolean equals(Object obj)
{
return true;
}
}
3.Map访问语句备忘
public static void print(Map map)
{
Set set = map.entrySet();
Iterator iter = set.iterator();
while(iter.hasNext())
{
Map.Entry entry = (Map.Entry)iter.next();
entry.getKey();
entry.getValue();
}
}