Map 接口

◈ 实现 Map 接口的类用来存储 键 - 值 对。
◈ Map 接口的实现类有HashMap 和 TreeMap 等。
◈ Map 类中存储的 键 - 值 对通过键来标识，所以键值不能重复。

object put (object key , object value);
object get (object key);
object remove (object key);
boolean containsKey (object key);
boolean containsValue (object value);
int size ();
boolean isEmpty ();
void putAll (Map t);
void clear ();


import java.util.*; public class Test { public static void main(String[] args) { Map m1 = new HashMap(); Map m2 = new TreeMap(); m1.put("one",new Integer(1)); m1.put("tow",new Integer(2)); m1.put("three",new Integer(3)); m2.put("A",new Integer(1)); m2.put("B",new Integer(2)); System.out.println(m1.size()); System.out.println(m1.containsKey("one")); System.out.println(m2.containsValue(new Integer(1))); if(m1.containsKey("two")) { int i = ((Integer)m1.get("two")).intValue(); } Map m3 = new HashMap(m1); m3.putAll(m2); System.out.println(m3); } }