//1.創(chuàng)建一個學(xué)生類，包含學(xué)生編號，姓名，性別，成績，將學(xué)生放入類集合中，添加5名學(xué)生，算出學(xué)生的平均成績

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", "詩名", '男', 95);

student A2 = new student("1_31", "書名", '男', 92);

student A3 = new student("4_52", "畫名", '男', 90);

student A4 = new student("2_22", "唱名", '男', 111);

student A5 = new student("6_66", "帥名", '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("學(xué)生的平均成績:" + 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.在第一題的基礎(chǔ)上，讓用戶輸入學(xué)生編號，修改學(xué)生的成績

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", "詩名", '男', 95));

arr.add(new student("1_31", "書名", '男', 92));

arr.add(new student("4_52", "畫名", '男', 90));

arr.add(new student("2_22", "唱名", '男', 111));

arr.add(new student("6_66", "帥名", '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("請輸入學(xué)生編號");

String bianhao = rongqi.next();

System.out.println("請輸入修改的成績");

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 "編號:" + ID + ",\t名字:" + name + ",\t性別:" + sex + ",\t成績:"

+ ChengJi;

}

}

//3.查詢編號為3的學(xué)生存不存在，如果不存在，添加該學(xué)生姓名和張三，男，88，如果存在則刪除編號為3的學(xué)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, "詩名", '男', 95));

arr.add(new student(2, "書名", '男', 92));

arr.add(new student(3, "畫名", '男', 90));

arr.add(new student(4, "唱名", '男', 111));

arr.add(new student(5, "帥名", '男', 134));

boolean b = true;

for (int i = 0; i < arr.size(); i++) {

if (arr.get(i).bianhao == 3) {

System.out.println("已經(jīng)找到該學(xué)生，執(zhí)行刪除編號為3的學(xué)生的信息功能");

arr.remove(i);

b = false;

break;

}

}

if (b) {

System.out.println("沒找到該學(xué)生，執(zhí)行添加“3, “張三”, '男', 88”功能");

student s = new student(3, "張三", '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 "編號:" + bianhao + ",\t名字:" + name + ",\t性別:" + sex + ",\t成績:"

+ ChengJi;

}

}