通过keySet方法和get方法遍历map中的每一个value

package imooc_collection_map;import java.util.HashSet;import java.util.Set;public class Student {public String id;public String name;public Set course;public Student(String id,String name){this.id=id;this.name=name;this.course=new HashSet();}}package imooc_collection_map;import
java.util.HashMap;import java.util.Map;import java.util.Scanner;import java.util.Set;public class MapTest {public Map students;//在构造器中初始化students属性 public MapTest(){this.students=new HashMap();}//测试添加，输入学生ID，判断学生ID是否已被占用//若未被占用，则输入姓名，创建学生对象，并添加到students中private
void pubTest() {// TODO Auto-generated method stubScanner scanner=new Scanner(System.in);int i=0;while(i<3){System.out.println("请输入学生ID:");String ID=scanner.next();Student student=students.get(ID);if (student==null) {System.out.println("请输入学生姓名：");// Scanner
scanner2=new Scanner(System.in);String st=scanner.next();Student newStudent=new Student(ID, st);students.put(ID, newStudent);System.out.println("成功添加学生："+students.get(ID).name);;i++;}else{System.out.println("该学生ID已被占用！");continue;}}}public void keySetTest()
{//通过keyset方法，返回Map中的所有“键”的set集合；Set keySet=students.keySet();int sts=students.size();System.out.println("总共有"+sts+"名学生！");//遍历keyset，取得每一个键，再调用get方法取得的每个键所对应的valuefor(String stID:keySet){Student st=students.get(stID);if(st!=null){System.out.println("学生："+st.name);}}}public
static void main(String[] args) {// TODO Auto-generated method stubMapTest mapTest=new MapTest();mapTest.pubTest();mapTest.keySetTest();}}