Judge whether the map contains the specified key and value

rewrite name Of hashcode() and equals() Method

package com.imooc.collection;

import java.util.HashSet;
import java.util.Set;
/** *  Students  * @author Monica * */

public class Student {
    
    public String id;
    public String name;
    public Set<Course> courses;
    public Student(String id,String name){
        this.id = id;
        this.name = name;
        this.courses = new HashSet<Course>();//set Interface call 
    }
    @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;
    }

}

package com.imooc.collection;

import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Scanner;
import java.util.Set;

public class MapTest {
    
    /** *  Used to hold student type objects  * @param args */
    public Map<String,Student> students;

    /** *  Try it out in the construction method students attribute  * @param args */
    public MapTest(){
        this.students = new HashMap<String,Student>();
    }
    /** *  Test add ： Enter the students ID, Determine whether it is occupied  *  If not occupied , Then enter the name , Create a new student object , And add to students in  * @param args */
    public void testPut(){
        // Create a Scanner object , Students used to get input ID And name 
        Scanner console = new Scanner(System.in);
        int i = 0;
        while (i<3){
            System.out.println(" Please input the students ID：");
            String ID = console.next();
            // Judge that ID Is it occupied 
            Student st = students.get(ID);
            if(st==null){
                System.out.println(" Please enter the student's name ：");
                String name = console.next();
                // Create a new student object 
                Student newStudent = new Student(ID,name);
                // By calling students Of put Method , add to ID- Student mapping 
                students.put(ID, newStudent);
                System.out.println(" Successfully added students ："+students.get(ID).name);
                i++;
            }else{
                System.out.println(" The student ID Occupied ！");
                continue;
            }
        }
    }
    /** *  test Map Does it contain a Key Value or value value  */
    public void testContainsKeyOrValue(){
        // Prompt for student id
        System.out.println(" Please enter the student to query ID：");
        Scanner console = new Scanner(System.in);
        String id = console.next();
        // stay Map in , use containsKey() Method , To determine whether it contains a Key value 
        System.out.println(" The student you entered ID by ："+id+", Whether there exists in the student mapping table ："+students.containsKey(id));
        if(students.containsKey(id))
            System.out.println(" The corresponding students are ："+students.get(id).name);
        // Prompt for student name 
        System.out.println(" Please enter the name of the student you want to query ：");
        String name = console.next();
        // stay containsValue() Method , To determine whether it contains a Value value 
        if(students.containsValue(new Student(null,name)))
            System.out.println(" In the student mapping table , It does include students ："+name);
        else
            System.out.println(" The student does not exist in the student mapping table ！");

    }
    /** *  test Map Of keySet Method  * @param args */
    public void testKeySet(){
        // adopt keySet Method , return Map All in “ key ” Of Set aggregate 
        Set<String> keySet = students.keySet();
        // obtain Map The capacity of , call set Method 
        System.out.println(" All in all "+keySet.size()+" A student ");
        // By traversing KeySet object , Get every key , Calling get Method to get the... Corresponding to each key value
        for(String stuId:keySet){
            Student st = students.get(stuId);
            if(st!=null)
                System.out.println(" Student ："+st.name);
        }
    }
    /** *  Test to delete Map Mapping in  * @param args */
    public void testRemove(){

        // Get the student to be deleted entered from the keyboard Id character string 
        Scanner console = new Scanner(System.in);
        while(true){
            // Prompt for the name of the student to be deleted ID 
            System.out.println(" Please enter the students you want to delete ID！");
            String ID = console.next();
            // Judge that ID Whether there is a corresponding student object 
            Student st = students.get(ID);
            if(st==null){
                // Prompt for ID There is no such thing as 
                System.out.println(" The ID non-existent ！");
                continue;
            }else{
                students.remove(ID);
                System.out.println(" Successfully deleted student ："+st.name);
                break;
            }
        }
    }
    /** *  adopt entrySet Method to traverse Map * @param args */
    public void testEntrySet(){
        // adopt entrySet Method , return Map All key value pairs in 
        Set<Entry<String,Student>> entrySet = students.entrySet();
        for(Entry<String,Student> entry:entrySet){
            System.out.println(" Get key ："+entry.getKey());
            System.out.println(" The corresponding value is ："+entry.getValue().name);
        }
    }
    /** *  utilize put Methods to modify Map Mapping already exists in  * @param args */
    public void testModify(){
        // Prompt for the student to modify Id
        System.out.println(" Please enter the student you want to modify ID：");
        // Create a Scanner object , To get students who input from the keyboard ID character string 
        Scanner console = new Scanner(System.in);
        while(true){
            // Get the student input from the keyboard ID
            String stuID = console.next();
            // from students Find the student in ID Corresponding student object 
            Student student = students.get(stuID);
            if(student == null){
                System.out.println(" The ID non-existent ！ Please re-enter ！");
                continue;
            }
            // Prompt the name of the current corresponding student object 
            System.out.println(" At present, the student ID, The corresponding students are ："+student.name);
            // Prompt for new student name , To modify the existing mapping 
            System.out.println(" Please enter a new student name ：");
            String name = console.next();
            Student newStudent = new Student(stuID,name);
            students.put(stuID, newStudent);
            System.out.println(" Modification successful ！");
            break;
        }
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        MapTest mt = new MapTest();
        mt.testPut();
        mt.testKeySet();
        //mt.testRemove();
        //mt.testEntrySet();
        //mt.testModify();
        //mt.testEntrySet();
        mt.testContainsKeyOrValue();
    }

}