HashMap遍历性能对比

</pre><pre name="code" class="java">public static void main(String[] args) {
Map<String, String> map = new TreeMap<String, String>();
int num = 1000000;
String key, value;
// 存放100万条数据
for (int i = 1; i <= num; i++) {
key = "" + i;
value = "value";
map.put(key, value);

}
// -------------------遍历 方法时间比较--------------------
long s = System.currentTimeMillis();
Iterator<String> iter1 = map.keySet().iterator();
while (iter1.hasNext()) {
key = iter1.next();
value = map.get(key);
}
// 测试时间：200
for (String key1 : map.keySet()) {
value = map.get(key1);
}
// 测试时间：219
Iterator<Entry<String, String>> iter2 = map.entrySet().iterator();
Entry<String, String> entry;
while (iter2.hasNext()) {
entry = iter2.next();
key = entry.getKey();
value = entry.getValue();
}
// 测试时间：41
for (Entry<String, String> entry1 : map.entrySet()) {
key = entry1.getKey();
value = entry1.getValue();
}
// 测试时间：40
long e = System.currentTimeMillis();
System.out.println("测试时间：" + (e - s));

}