Java中HashMap遍历几种方式

第一种：

       HashMap hashmap = new HashMap();
        for (int i = 0; i < 100000; i++) {
            hashmap.put("" + i, "thanks");
        }
        long bs = Calendar.getInstance().getTimeInMillis();
        Iterator iterator = hashmap.keySet().iterator();
        while (iterator.hasNext()) {
            System.out.print(hashmap.get(iterator.next()));
        }
        System.out.println();
        CLog.i(TAG, "keySet time: " + (Calendar.getInstance().getTimeInMillis() - bs));
        // 100000次，用时：keySet time: 36650
        System.out.println();

第二种(效率高)：

       HashMap hashmap1 = new HashMap();
        for (int i = 0; i < 100000; i++) {
            hashmap1.put("" + i, "thanks");
        }
        long bs1 = Calendar.getInstance().getTimeInMillis();
        Iterator it = hashmap1.entrySet().iterator();
        while (it.hasNext()) {
            java.util.Map.Entry entry = (java.util.Map.Entry) it.next();
            // entry.getKey() 返回与此项对应的键
            // entry.getValue() 返回与此项对应的值
            System.out.print(entry.getValue());
        }
        System.out.println();
        CLog.i(TAG, "entrySet time: " + (Calendar.getInstance().getTimeInMillis() - bs1));
        // 100000次 用时：36816

话说第二种效率高，其实实测了下，貌似差不多，大家可以将次数加几个数量级在比较一下