Map集合用于存储元素对(即存储的是一对键值),是通过key映射到它的键值value。
public class Test3 {
public static void main(String[] args) {
Map m = new HashMap();
m.put("aaa",new Student(1232,"张三"));
m.put("baa",new Student(1232,"王五"));
m.put("caa",new Student(1232,"赵四"));
//取value
System.out.println(m.get("aaa"));
//取key和value
Set s = m.entrySet();
Iterator iter = s.iterator();
while(iter.hasNext()){
Map.Entry entry = (Map.Entry) iter.next();
System.out.println(entry.getKey() + ":" + entry.getValue());
}
//取所有的值
Collection c = m.values();
Iterator it = c.iterator();
while (it.hasNext()){
System.out.println(it.next());
}
//取所有的键
Set ss = m.keySet();
Iterator iter1 = ss.iterator();
while(iter1.hasNext()){
System.out.println(iter1.next());
}
}
}
输出结果: