HashMap遍历 key value
2015-09-15 23:21
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 | HashMap遍历的两种方式: 第一种: Map map = new HashMap(); Iterator iter = map.entrySet().iterator(); while (iter.hasNext()) { Map.Entry entry = (Map.Entry) iter.next(); Object key = entry.getKey(); Object val = entry.getValue(); }效率高,推荐使用此种方式! 第二种: Map map = new HashMap(); Iterator iter = map.keySet().iterator(); while (iter.hasNext()) { Object key = iter.next(); Object val = map.get(key); } 效率低比第一种要低,不推荐使用!public class HashMapTest { public static void main(String[] args) { HashMap hashmap = new HashMap(); for (int i = 0; i < 1000; 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(); System.out.println(Calendar.getInstance().getTimeInMillis() - bs); listHashMap(); } public static void listHashMap(){ java.util.HashMap hashmap = new java.util.HashMap(); for (int i = 0; i < 1000; i++ ){ hashmap.put(i, "thanks"); } long bs = Calendar.getInstance().getTimeInMillis(); java.util.Iterator it = hashmap.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(); System.out.println(Calendar.getInstance().getTimeInMillis() - bs); } } |
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