遍曆map-Java基礎

2011-1-6 java遍曆map所有元素

//JDK1.5後Map map = getMap();  for(Object obj : map.keySet()) {    Object key = obj;    Object value = map.get(obj);}//JDK1.5之前Map map =  getMap();Iterator iter = map.entrySet().iterator();    while(iter.hasNext()) {    Map.Entry entry = (Map.Entry)iter.next();    Object key = entry.getKey();    Object value = entry.getValue();}

 

遍曆K-V

 

/* 第一種: entryset只遍曆一次:它把key和value放到entry */Map map = getMap();Iterator iter = map.entrySet().iterator();while (iter.hasNext()) {    Map.Entry entry = (Map.Entry) iter.next();    Object key = entry.getKey();    Object val = entry.getValue();}//高效,使用此種方式/* 第二種: keySet實際遍曆了2次：轉為iterator時候一次；取key對應value又一次。*/Map map = getMap();Iterator iter = map.keySet().iterator();while (iter.hasNext()) {    Object key = iter.next();    Object val = map.get(key);}//效率低