@Override
 public int hashCode() {
  final int prime = 31;
  int result = 1;
  result = prime * result + ((name == null) ? 0 : name.hashCode());
  return result;
 }
 @Override
 public boolean equals(Object obj) {
  if (this == obj)
   return true;
  if (obj == null)
   return false;
  if (!(obj instanceof Student))
   return false;
  Student other = (Student) obj;
  if (name == null) {
   if (other.name != null)
    return false;
  } else if (!name.equals(other.name))
   return false;
  return true;
 }

public void testContainsKeyOrValue() {
  //提示输入学生ID
  System.out.println("请输入要查询的学生ID");
  Scanner sc=new Scanner(System.in);
  String id=sc.next();
  //用ContainsKey判断
  System.out.println("您输入的学生ID为"+id+"在学生映射表中是否存在"
  +students.containsKey(id));
  if(students.containsKey(id)) {
   System.out.println("对应学生为："+students.get(id).name);
  }
  //提示输入学生姓名
  System.out.println("请输入要查询的学生姓名");
  String name=sc.next();
  //用ContainsValue方法来判断是否存在输入的学生姓名
  if(students.containsValue(new Student("null","name"))) {
   System.out.println("映射表中包含学生"+name);
  }else {
   System.out.println("该学生不存在");
  }
 }