Map 映射

package lis0924;
 
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.TreeMap;
 
public class Text04 {
 
	public static void main(String[] args) {
 
		//map
 
		Map<String, String> m1=new HashMap<>();
		//添加数据
		//Key不能重复
		//value可以重复
		m1.put("0531", "济南");
		m1.put("0532", "青岛");
		m1.put("0533", "淄博");
		m1.put("0531", "章丘");//如果key重复，新的value覆盖旧的value
		m1.put("0530", "章丘");
 
		//System.out.println(m1);
		//长度
		System.out.println("size="+m1.size());
		//获取数据
		System.out.println("0531="+m1.get("0531"));
		System.out.println("0530="+m1.get("0530"));
 
		//移除
		m1.remove("0530");
		System.out.println("size="+m1.size());
		System.out.println("0530="+m1.get("0530"));
 
		System.out.println("key是否存在="+m1.containsKey("0533"));
 
		System.out.println("value是否存在="+m1.containsValue("淄博"));
 
		//遍历
		//通过遍历key的set集合，同时获取value
		System.out.println("foreach方式：");
		for(String k:m1.keySet())
		{
			System.out.println("key="+k+"value="+m1.get(k));
		}
		System.out.println("TreeMap");
		//TreeMap
		TreeMap<Integer, Person> tm=new TreeMap<>();
		tm.put(100, new Person("x",20));
		tm.put(103, new Person("A",20));
		tm.put(110, new Person("B",20));
		tm.put(10, new Person("B",20));
		tm.put(210, new Person("B",20));
		//遍历
		for(Integer k:tm.keySet())//通过遍历key的set集合赋值给k，同时获取value
		{
			System.out.println("key="+k+"value="+tm.get(k));//通过读k，也就是读key来获取value
		}
 
	}
 
}