java.util（一）HashMap TreeMap TreeSet

import java.util.*;

public class TestMap01 {
public static void main(String[] args) {
// Create a HashMap
Map<String, Integer> hashMap = new HashMap<String, Integer>();
hashMap.put("Smith", 30);
hashMap.put("Anderson", 31);
hashMap.put("Lewis", 29);
hashMap.put("Cook", 29);

System.out.println("Display entries in HashMap");
System.out.println(hashMap);

// Create a TreeMap from the previous HashMap
Map<String, Integer> treeMap =
new TreeMap<String, Integer>(hashMap);
System.out.println("\nDisplay entries in ascending order of key");
System.out.println(treeMap);

//    TreeSet<String> name=treeMap.keySet();
TreeSet<String> name=new TreeSet<String>(treeMap.keySet());
System.out.println(name);

TreeSet<Integer> age=new TreeSet<Integer>(treeMap.values());
System.out.println(age);

Set<Map.Entry<String, Integer>> entrySet = treeMap.entrySet();

// Get key and value from each entry
for (Map.Entry<String, Integer> entry: entrySet)
System.out.println( entry.getKey()+ "\t" + entry.getValue());
}
}