public class MapTest {

public Map<String, Student> students;

public MapTest() {

this.students = new HashMap();

}

public void mapAdd() {

Scanner console = new Scanner(System.in);

int i = 0;

while (i < 3) {

System.out.println("请输入学生ID:");

String ID = console.next();

Student stu = students.get(ID);

if (stu == null) {

System.out.println("input student's name:");

String name = console.next();

Student newStudent = new Student(ID, name);

students.put(ID, newStudent);

System.out.println("成功添加:" + students.get(ID).name);

i++;

} else {

System.out.println("已经存在ID再输：");

continue;

}

}

testKeySet();

}

public void testKeySet() {

Set<String> keySet = students.keySet();

for (String stuId : keySet) {

Student stu = students.get(stuId);

if (stu != null) {

System.out.print(stu.name);

}

}

}

public static void main(String[] args) {

MapTest mt = new MapTest();

mt.mapAdd();

}

}

请输入学生ID:

1

input student's name:

tom

成功添加:1

请输入学生ID:

2

input student's name:

jay

成功添加:2

请输入学生ID:

3

input student's name:

jack

成功添加:3

123