java Map 遍历方法2009-05-02 10:56
JDK1.4中
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
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。
private Hashtable
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//方法一: 用entrySet()
Iterator it = emails.entrySet().iterator();
while(it.hasNext()){
Map.Entry m=(Map.Entry)it.next();
https://www.wendangku.net/doc/a97897147.html,("email-" + m.getKey() + ":" + m.getValue());
}
// 方法二:jdk1.5支持,用entrySet()和For-Each循环()
for (Map.Entry
https://www.wendangku.net/doc/a97897147.html,("email-" + m.getKey() + ":" + m.getValue()); }
// 方法三:用keySet()
Iterator it = emails.keySet().iterator();
while (it.hasNext()){
String key;
key=(String)it.next();
https://www.wendangku.net/doc/a97897147.html,("email-" + key + ":" + emails.get(key));
}
// 方法五:jdk1.5支持,用keySEt()和For-Each循环
for(Object m: emails.keySet()){
https://www.wendangku.net/doc/a97897147.html,("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
public static void main(String[] args) {
ArrayList
HashMap
TreeMap
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
//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));
}
}