hashMap的遍历

今天写的一个算法中用到了hashMap，于是将其学习一下

普通HashMap的遍历

HashMap<String,String> student=new HashMap<String,String>();
        student.put("a", "grade 1");
        student.put("b", "grade 2");
        student.put("c", "grade 3");
        Iterator it=student.keySet().iterator();
        while(it.hasNext())
        {
            String m=(String)it.next();
            System.out.println("key="+m+" value="+student.get(m));
        }
        //第二种
        Set<Entry<String, String>> sets = student.entrySet();  
        for(Entry<String, String> entry : sets) {  
            System.out.print(entry.getKey() + ", ");  
            System.out.println(entry.getValue());  
        }  
        //第三种
        HashMap<String,Integer> studentScore=new HashMap<String,Integer>();
        studentScore.put("a", 98);
        studentScore.put("b", 78);
        studentScore.put("c", 89);
        Iterator iit=studentScore.keySet().iterator();
        while(iit.hasNext())
        {
            String m=(String)iit.next();
            System.out.println("key="+m+" value="+studentScore.get(m));
        }

含有HashMap的value是ArrayList时

Iterator<Entry<String, ArrayList<TreeNode>>> it = linkedNode.entrySet().iterator();
                while( it.hasNext())
                {
                    Map.Entry<String, ArrayList<TreeNode>> entry = it.next();
                    String key = entry.getKey();
                    ArrayList<TreeNode> values=(ArrayList<TreeNode>)entry.getValue();
                    for(TreeNode value:values)
                    {
                        System.out.print(" name="+value.getName()+" count="+value.getCount());
                    }
                    System.out.println();
                    //TreeNode tempNode= entry.getValue().get(i);
                }