Java（改进）：学生类，集合，转换，修改成绩，查询编号为3的学生存不存在，添加删除
//1.创建一个学生类，包含学生编号，姓名，性别，成绩，将学生放入类集合中，添加5名学生，算出学生的平均成绩
package a;
import java.util.ArrayList;
public class lizi {
public static void main(String[] arrgs) {
ArrayList s = new ArrayList();
student A1 = new student("5_20", "诗名", '男', 95);
student A2 = new student("1_31", "书名", '男', 92);
student A3 = new student("4_52", "画名", '男', 90);
student A4 = new student("2_22", "唱名", '男', 111);
student A5 = new student("6_66", "帅名", '男', 134);
s.add(A1);
s.add(A2);
s.add(A3);
s.add(A4);
s.add(A5);
double ChengJiZongHe = 0;
for (int i = 0; i < s.size(); i++) {
student k = (student) s.get(i);
ChengJiZongHe += k.chengji;
}
System.out.println("学生的平均成绩:" + ChengJiZongHe / s.size());
}
}
class student {
String ID;
String name;
char sex;
double chengji;
public student(String ID, String name, char sex, double chengji) {
this.ID = ID;
this.name = name;
this.sex = sex;
this.chengji = chengji;
}
}
// 2.在第一题的基础上，让用户输入学生编号，修改学生的成绩
package a;
import java.util.ArrayList;
import java.util.Scanner;
public class lizi {
public static void main(String[] args) {
ArrayList<student> arr = new ArrayList<student>();
arr.add(new student("5_20", "诗名", '男', 95));
arr.add(new student("1_31", "书名", '男', 92));
arr.add(new student("4_52", "画名", '男', 90));
arr.add(new student("2_22", "唱名", '男', 111));
arr.add(new student("6_66", "帅名", '男', 134));
for (int i = 0; i < arr.size(); i++) {
System.out.println(arr.get(i).toString());
}
Scanner rongqi = new Scanner(System.in);
System.out.println("请输入学生编号");
String bianhao = rongqi.next();
System.out.println("请输入修改的成绩");
double xiugaihoudechengji = rongqi.nextDouble();
for (int i = 0; i < arr.size(); i++) {
student k = arr.get(i);
if (k.ID.equals(bianhao)) {
k.ChengJi = xiugaihoudechengji;
}
}
double sum = 0;
for (int i = 0; i < arr.size(); i++) {
student k = arr.get(i);
sum += k.ChengJi;
}
for (int i = 0; i < arr.size(); i++) {
System.out.println(arr.get(i).toString());
}
}
}
class student {
double ChengJi;
String ID;
String name;
char sex;
public student(String ID, String name, char sex, double ChengJi) {
this.ID = ID;
this.name = name;
this.sex = sex;
this.ChengJi = ChengJi;
}
@Override
public String toString() {
return "编号:" + ID + ",\t名字:" + name + ",\t性别:" + sex + ",\t成绩:"
+ ChengJi;
}
}
//3.查询编号为3的学生存不存在，如果不存在，添加该学生姓名和张三，男，88，如果存在则删除编号为3的学生的信息
package a;
import java.util.ArrayList;
public class lizi {
public static void main(String[] args) {
ArrayList<student> arr = new ArrayList<student>();
arr.add(new student(1, "诗名", '男', 95));
arr.add(new student(2, "书名", '男', 92));
arr.add(new student(3, "画名", '男', 90));
arr.add(new student(4, "唱名", '男', 111));
arr.add(new student(5, "帅名", '男', 134));
boolean b = true;
for (int i = 0; i < arr.size(); i++) {
if (arr.get(i).bianhao == 3) {
System.out.println("已经找到该学生，执行删除编号为3的学生的信息功能");
arr.remove(i);
b = false;
break;
}
}
if (b) {
System.out.println("没找到该学生，执行添加“3, “张三”, '男', 88”功能");
student s = new student(3, "张三", '男', 88);
arr.add(s);
}
for (student j : arr) {
System.out.println(j);
}
}
}
class student {
int bianhao;
double ChengJi;
String name;
char sex;
public student(int bianhao, String name, char sex, double ChengJi) {
this.bianhao = bianhao;
this.name = name;
this.sex = sex;
this.ChengJi = ChengJi;
}
@Override
public String toString() {
return "编号:" + bianhao + ",\t名字:" + name + ",\t性别:" + sex + ",\t成绩:"
+ ChengJi;
}
}
