案例-学生成绩管理

一共需要创建三个类:
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 {
	// 创建全局的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,获取到所有学生的成绩,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() {

		//创建一个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();   //用集合接收获取所有的键
		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) {
		
		//先创建一个对象
		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();
		
	}

}