Java如何遍历Map的所有的元素

来源：互联网发布：java有多少个类编辑：程序博客网时间：2024/05/01 16:14

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,应用新特性For-Each循环

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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 中的每个元素都是一个 Map.Entry 类型。

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private Hashtable<String, String> emails =new Hashtable<String, String>();

private Hashtable<String, String> emails = new Hashtable<String, String>();

另外我们可以先把hashMap 转为集合Collection，再迭代输出，不过得到的对象

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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循环()
for (Map.Entry<String, String> 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循环
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循环()   for (Map.Entry<String, String> 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循环for(Object m: emails.keySet()){    logger.info("email-" + m+ ":" + emails.get(m));   }

Map aa = new HashMap(); aa.put("tmp1", new Object()); //追加替换用同样的函数. aa.remove("temp1"); //删除 for (Iterator i = aa.values().iterator(); i.hasNext(); ) { Object temp = i.next(); } //遍历

来个完整的，包含TreeSet的元素内部排序的

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public staticvoid main(String[] args) {
ArrayList<String> list = new ArrayList<String>();
HashMap<Object,Object> hash = new HashMap<Object,Object>();
TreeMap<Object,Object> treeMap = new TreeMap<Object,Object>();
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遍历
for(String m: list){
System.out.println(m);
}
// hashmap entrySet() 遍历
for(Map.Entry<Object,Object> m: hash.entrySet()){
System.out.println(m.getKey()+"---"+m.getValue());
}
//hashmap keySet() 遍历
for(Object m: hash.keySet()){
System.out.println(m+"---"+hash.get(m));
}
// treemap keySet()遍历
for(Object m: treeMap.keySet()){
System.out.println(m+"---"+treeMap.get(m));
}
}

以上内容转自网络：http://blog.csdn.net/szwangdf/article/details/2544143

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