对于Map<key,value> :
(1)key不允许重复,value的值允许重复;
(2)向map中添加元素,成功返回null,失败返回value的值;
Map最常用的遍历方式:
(1)
Map<String, String> map = new HashMap<String, String>();
map.put("str1", "aaaaaaaaaa");
map.put("str2", "bbbbbbbbb");
for (Map.Entry<String, String> entry : map.entrySet()) {
String mapKey = entry.getKey();
String mapValue = entry.getValue();
System.out.println(mapKey + ":" + mapValue);
}
(2)
Map<String, String> map = new HashMap<String, String>();
map.put("str1", "aaaaaaaaaa");
map.put("str2", "bbbbbbbbb");
Iterator<Map.Entry<String String>> it = map.entrySet().iterator();
while (it.hasNext()) {
Map.Entry<String, String> entry = it.next();
System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());
}
(3)
Map<String, String> map = new HashMap<String, String>();
map.put("str1", "aaaaaaaaaa");
map.put("str2", "bbbbbbbbb");
for (String key : map.keySet()) {
System.out.println(key+map.get(key));
}