Java中怎樣遍歷Map的所有的元素

JDK1.4中

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Map map = new HashMap();

Iterator it = map.entrySet().iterator();

while (it.hasNext()) {

Map.Entry entry = (Map.Entry) it.next();

Object key = entry.getKey();

Object value = entry.getValue();

}

Map map = new HashMap();

Iterator it = map.entrySet().iterator();

while (it.hasNext()) {

Map.Entry entry = (Map.Entry) it.next();

Object key = entry.getKey();

Object value = entry.getValue();

}JDK1.5中,應用新特性For-Each循環

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Map m = new HashMap();

for(Object o : map.keySet()){

map.get(o);

}

Map m = new HashMap();

for(Object o : map.keySet()){

map.get(o);

}返回的 set 中的每個元素都是一個 Map.Entry 類型。

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private Hashtable emails = new Hashtable();

private Hashtable emails = new Hashtable();? 另外 我們可以先把hashMap 轉為集合Collection，再迭代輸出，不過得到的對象

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//方法一: 用entrySet()

Iterator it = emails.entrySet().iterator();

while(it.hasNext()){

Map.Entry m=(Map.Entry)it.next();

logger.info("email-" + m.getKey() + ":" + m.getValue());

}

// 方法二：jdk1.5支持，用entrySet()和For-Each循環()

for (Map.Entry m : emails.entrySet()) {

logger.info("email-" + m.getKey() + ":" + m.getValue());

}

// 方法三：用keySet()

Iterator it = emails.keySet().iterator();

while (it.hasNext()){

String key;

key=(String)it.next();

logger.info("email-" + key + ":" + emails.get(key));

}

// 方法五：jdk1.5支持，用keySEt()和For-Each循環

for(Object m: emails.keySet()){

logger.info("email-" + m+ ":" + emails.get(m));

}

//方法一: 用entrySet()

Iterator it = emails.entrySet().iterator();

while(it.hasNext()){

Map.Entry m=(Map.Entry)it.next();

logger.info("email-" + m.getKey() + ":" + m.getValue());

}

// 方法二：jdk1.5支持，用entrySet()和For-Each循環()

for (Map.Entry m : emails.entrySet()) {

logger.info("email-" + m.getKey() + ":" + m.getValue());

}

// 方法三：用keySet()

Iterator it = emails.keySet().iterator();

while (it.hasNext()){

String key;

key=(String)it.next();

logger.info("email-" + key + ":" + emails.get(key));

}

// 方法五：jdk1.5支持，用keySEt()和For-Each循環

for(Object m: emails.keySet()){

logger.info("email-" + m+ ":" + emails.get(m));

}

Map??? aa??? =??? new??? HashMap();????? aa.put("tmp1",??? new??? Object());????? //追加????? 替換用同樣的函數.????? aa.remove("temp1");??????????????????????? //刪除????? for??? (Iterator??? i??? =??? aa.values().iterator();??? i.hasNext();??? )??? {????????????? Object??? temp??? =??? i.next();????? }????????? //遍歷

來個完整的，包含TreeSet的元素內部排序的

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public static void main(String[] args) {

ArrayList list = new ArrayList();

HashMap hash = new HashMap();

TreeMap treeMap = new TreeMap();

list.add("a");

list.add("b");

list.add("c");

hash.put(3, 3);

hash.put(4, 4);

hash.put(5, 5);

hash.put(6, 6);

hash.put(1, 1);

hash.put(2, 2);

treeMap.put(1, 1);

treeMap.put(2, 2);

treeMap.put(3, 3);

treeMap.put(4, 4);

treeMap.put(5, 5);

treeMap.put(6, 6);

//list遍歷

for(String m: list){

System.out.println(m);

}

// hashmap entrySet() 遍歷

for(Map.Entry m: hash.entrySet()){

System.out.println(m.getKey()+"---"+m.getValue());

}

//hashmap keySet() 遍歷

for(Object m: hash.keySet()){

System.out.println(m+"---"+hash.get(m));

}

// treemap keySet()遍歷

for(Object m: treeMap.keySet()){

System.out.println(m+"---"+treeMap.get(m));

}

}

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