案例-学生成绩管理

一共须要建立三个类:
1:Student类------存放程序所需的属性和方法
2:Control类------具体的实现方法
3:Test类------测试类

Student类

import java.util.ArrayList;

public class Student {

    String name;
    int id;
    ArrayList<Subject> list;
    
    public Student() {
        
    }
    
    public Student(String name,int id,ArrayList<Subject> list) {
        this.name = name;
        this.id = id;
        this.list = list;
    }

    @Override
    public String toString() {
        return "Student [name=" + name + ", id=" + id + ", list=" + list + "]";
    }
}

class Subject {
    String name;
    int score;
    
    public Subject() {
        
    }
    public Subject(String name,int score) {
        this.name = name;
        this.score = score;
    }

    @Override
    public String toString() {
        return "Subject [name=" + name + ", score=" + score + "]";
    }
    
}

Control类

import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;

import javax.swing.text.html.HTMLDocument.Iterator;

public class Control {
    // 建立全局的list
    LinkedList<Student> list = new LinkedList<Student>();
    void initStudent() {
        Subject subject1 = new Subject("语文",90);
        Subject subject2 = new Subject("数学",80);
        Subject subject3 = new Subject("英语",88);
        ArrayList<Subject> list1 = new ArrayList<Subject>();
        list1.add(subject1);
        list1.add(subject2);
        list1.add(subject3);
        Student student1 = new Student("张三",1,list1);

        Subject subject11 = new Subject("语文",66);
        Subject subject21 = new Subject("数学",65);
        Subject subject31 = new Subject("英语",99);
        ArrayList<Subject> list2 = new ArrayList<Subject>();
        list2.add(subject11);
        list2.add(subject21);
        list2.add(subject31);
        Student student2 = new Student("李四",2,list2);

        Subject subject12 = new Subject("语文",78);
        Subject subject22 = new Subject("数学",88);
        Subject subject32 = new Subject("英语",89);
        ArrayList<Subject> list3 = new ArrayList<Subject>();
        list3.add(subject12);
        list3.add(subject22);
        list3.add(subject32);
        Student student3 = new Student("王五",3,list3);

        Subject subject13 = new Subject("语文",66);
        Subject subject23 = new Subject("数学",88);
        Subject subject33 = new Subject("英语",56);
        ArrayList<Subject> list4 = new ArrayList<Subject>();
        list4.add(subject13);
        list4.add(subject23);
        list4.add(subject33);
        Student student4 = new Student("赵六",4,list4);

        Subject subject14 = new Subject("语文",66);
        Subject subject24 = new Subject("数学",66);
        Subject subject34 = new Subject("英语",83);
        ArrayList<Subject> list5 = new ArrayList<Subject>();
        list5.add(subject14);
        list5.add(subject24);
        list5.add(subject34);
        Student student5 = new Student("温九",5,list5);

        this.list.add(student1);
        this.list.add(student2);
        this.list.add(student3);
        this.list.add(student4);
        this.list.add(student5);

    }


    //1,获取指定学生的成绩
    public void score(String name) {
        //遍历list中的学生
        for (Student student : this.list) {
            if (name.equals(student.name)) {
                List<Subject> subList = student.list;
                System.out.println(subList);
            }
        }
    }

    //2,获取指定学号的成绩
    public void idScore(int id) {
        for (Student student : this.list) {
            if (student.id == id) {
                System.out.println(student.list);
            }
        }
    }

    //3,根据学生的id修改姓名
    public void idChangeName(int id,String name) {
        for (Student student : this.list) {
            if (student.id == id) {
                System.out.println("修改前的学生的姓名是:" + student.name);
                student.name = name;
                System.out.println("修改后的学生的姓名是:" + student.name);
            }
        }
    }
    //4,根据姓名修改指定学科的成绩
    public void changeScore(String name,String sub,int score) {
        for (Student student : this.list) {
            if (student.name.equals(name)) {
                System.out.println("修改前学生的成绩是:" + student.list);
                for (Subject subject : student.list) {
                    if (subject.name.equals(sub)) {
                        subject.score = score;
                        System.out.println("修改后的学生的成绩是:" + student.list);
                    }
                }
            }
        }
    }
    //5,删除指定学生的成绩
    public void delete(String name) {
        for (Student student : this.list) {
            if (student.name.equals(name)) {
                this.list.remove();
                System.out.println("删除成功");
                for (Student student1 : this.list) {
                    System.out.println(student1);
                }
                return;
            }
        }
    }
    //6,获取到全部学生的成绩,映射到新的数组中,并进行排序
    public void getScore() {
        ArrayList<Integer> list1 = new ArrayList<Integer>();
        for (int i = 0; i < list.size(); i++) {
            Student stu = list.get(i);
            list1.add(stu.list.get(0).score);
        }
        System.out.println(list1);


        for (int i = 0; i < list1.size() - 1; i++) {
            for (int j = 0; j < list1.size()- i - 1; j++) {
                if (list1.get(j) > list1.get(j+1)) {
                    int temp = list1.get(j);
                    list1.set(j, list1.get(j+1));
                    list1.set(j+1, temp);
                }
            }
        }

        System.out.println(list1);
    }
    //7*统计一下相同成绩的人的人数
    public void number() {

        //建立一个HashMap来存放数组的信息,HashMap的键为元素，值为该元素出现的次数
        HashMap<Integer, Integer> map = new HashMap<Integer,Integer>();
        //从装学生的list中取出学生信息
        for (Student student : list) {
            //从装学科的list中取出各科成绩
            for (Subject subject : student.list) {
                //System.out.println(subject);
                if (subject.name == "语文") {
                    Integer num = map.get(subject.score);    
                    map.put(subject.score, num == null ? 1 : num + 1); 
                }    
            }
        }

        Set keySet = map.keySet();   //用集合接收获取全部的键
        for (Object object : keySet) {
            System.out.print("成绩:" + object);
            System.out.print(",");
            System.out.println("出现的次数: " + map.get(object));
        }

    }
}

Test类

import java.util.Scanner;
public class Test {

    public static void main(String[] args) {
        
        //先建立一个对象
        Control control = new Control();
        control.initStudent();
        //1,
        System.out.println("请输入学生的姓名:");
        Scanner sc = new Scanner(System.in);
        String name = sc.next();
        control.score(name);
        //2,
        System.out.println("请输入学生的id:");
        int id = sc.nextInt();
        control.idScore(id);
        
        //3,
        System.out.println("请输入学生的id:");
        int id1 = sc.nextInt();
        System.out.println("请输入要修改的姓名:");
        String name1 = sc.next();
        control.idChangeName(id1, name1);
        
        //4,
        control.changeScore("张三", "语文", 100);
        
        //5
        control.delete("张三");
        
        //6,
        control.getScore();
        
        //7,
        control.number();
        
    }

}