Java学习记录(补充二:面对对象基础复习,习题)

求3(可调整)个学员成绩的和或平均分或两者都具
package day5;

import java.util.Scanner;

public class Score {
    //构造函数
    public Score(){
        System.out.println("实例化对象调用了我");
    }
    int sum;
    double avg;
    // 定义求和的方法
    public int sum() {
        Scanner scanner = new Scanner(System.in);
        for (int i = 0; i < 3; i++) {
            System.out.println("请输入第" + (i + 1) + "个学员成绩");
            int score = scanner.nextInt();
            sum += score;
        }
        return sum;
    }
    //求平均分的方法    凡是方法名报错都是没有返回值return;
    public double avg(){
        double result = sum()/3;
        return result;
    }
    
    //既求和又求平均分的方法
    public double[] getSumAndAvg(){
        double[] results = new double[2];
        Scanner scanner = new Scanner(System.in);
        for (int i = 0; i < 3; i++) {
            System.out.println("请输入第" + (i + 1) + "个学员成绩");
            int score = scanner.nextInt();
            sum += score;
        }
        results[0] = sum;
        results[1] = sum/3;
        return results;
    }
    
}

package day5;

import java.util.Arrays;


public class ScoreCalc {
    public static void main(String[] args) {
        // 由类来产生对象 (实例化)会调用你的构造函数
        Score score1 = new Score();
        // 对象生成以后, 可以调用对象里的各个属性和方法
        
        System.out.println(score1.sum());
        System.out.println(Arrays.toString(score1.getSumAndAvg()));
    }
}

结果图:

求三门课的和及平均分(构造有参函数)
package day5_1;

public class Score {
    // 属性
    int math;// 数学成绩
    int chinese;// 语文成绩
    int english;// 英语成绩
    int sum;// 总分
    double avg;// 平均分

    // 构造函数 与类同名,没有返回值 作用:数据的初始化!!!
    public Score(int math, int chinese, int english) {
        this.math = math;
        this.chinese = chinese;
        this.english = english;
    }

    // 方法
    // 求和
    public int sum() {
        sum = math + chinese + english;
        return sum;
    }

    // 求平均分
    public double avg() {
        avg = (math + chinese + english) / 3.0;
        return avg;
    }
}

package day5_1;

import java.util.Scanner;

public class ScoreTest {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入数学成绩");
        int math = scanner.nextInt();
        System.out.println("请输入语文成绩");
        int chinese = scanner.nextInt();
        System.out.println("请输入英语成绩");
        int english = scanner.nextInt();
        //单纯的实例化对象
//        Score score = new Score();
//        score.math = math;
//        score.chinese = chinese;
//        score.english = english;
        
        //实例化兑现过的同时进行数据的初始化
        Score score = new Score(math,chinese,english);
        
        int result1 = score.sum();
        double result2 = score.avg();
        System.out.println(result1);
        System.out.println(result2);
    }
}

结果图:

学生名字排序(创建一个数组对象)
package day5_2;

import java.util.Arrays;

public class NameSort {
    //2:把方法封装
    public String[] sort(String[] unOrderArr) {
        Arrays.sort(unOrderArr);
        return unOrderArr;
    }
}

package day5_2;

import java.util.Arrays;
import java.util.Scanner;

public class NameSortTest {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        //1:准备数据
        String names[]= new String[5];
        for (int i = 0; i < 5; i++) {
            System.out.println("请一次输入第" + (i + 1) + "个学生名字");
            names[i] = scanner.next();
        }
        //3:调用类的方法(先实例化出对象)
        NameSort sortName = new NameSort();
        String[] orderArr = sortName.sort(names);
        System.out.println(Arrays.toString(orderArr));
    }
}

结果图:

单个对象的三门成绩求均分(传输对象)
package day5_2;

public class Student {
    int math;
    int chinese;
    int english;
    public Student(int math,int chinese,int english){
        this.math = math;
        this.chinese = chinese;
        this.english = english;
    }
}

package day5_2;

public class StudentCalc {
    //创建一个对象(Student)
    public double avg(Student student){
        int mathScore = student.math;
        int chineseScore = student.chinese;
        int englishScore = student.english;
        double avg = (mathScore+chineseScore+englishScore)/3;
        return avg;
    }
}

package day5_2;

import java.util.Scanner;

public class StudentTest {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入数学成绩");
        int math = scanner.nextInt();
        System.out.println("请输入语文成绩");
        int chinese = scanner.nextInt();
        System.out.println("请输入英语成绩");
        int english = scanner.nextInt();
        Student zhangSan = new Student(math, chinese, english);
        StudentCalc calc = new StudentCalc();
        System.out.println("平均分:"+calc.avg(zhangSan));
    }
}

结果图:

多个对象的姓名,年龄,身高,总身高平均(传输对象数组)
package day5_3;

(构造一个有参函数)
public class Student {
        String name;
        int age;
        int height;
        public Student(String name,int age,int height){
            this.name = name;
            this.age = age;
            this.height = height;
        }
        
}

package day5_3;

public class StudentManager {
    //创建一个对象数组(Student[])
    public int avg(Student[] students) {
        int sum = 0;
        for (int i = 0; i < students.length; i++) {
            sum += students[i].height;
        }
        return sum/students.length;
    }

}

package day5_3;

import java.util.Scanner;

public class StudentManagerTest {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        Student[] students = new Student[2];
        for (int i = 0; i < students.length; i++) {
            System.out.println("输入姓名");
            String name = scanner.next();
            System.out.println("请输入年龄");
            int age = scanner.nextInt();
            System.out.println("请输入身高");
            int height = scanner.nextInt();
            Student student = new Student(name, age, height);
            students[i] = student;
        }
        StudentManager calc = new StudentManager();
        System.out.println(calc.avg(students));
    }
}

结果图:

一次传递多个参数

package Day5_4;

public class User {
    String nick;
    String pwd;
    int age;
    String sex;
    String resignDate;
    String degree;
    public User(String nick,String pwd,int age,String sex,String resignDate,String degree){
        this.nick =nick;
        this.pwd = pwd;
        this.age = age;
        this.resignDate = resignDate;
        this.sex = sex;
        this.degree = degree;
    }
    public void  showMessage() {
        System.err.println("大家好!我是"+nick+",今年"+age+"岁");
        System.err.println("我是"+resignDate+"年注册的,目前等级是:"+degree);
        
    }
}

package Day5_4;

import java.util.Scanner;

public class UserTest {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入您的昵称:");
        String nick = scanner.next();
        System.out.println("请输入您的密码:");
        String pwd = scanner.next();
        System.out.println("请输入您的性别:");
        String sex = scanner.next();
        System.out.println("请输入您的等级:");
        String degree = scanner.next();
        System.out.println("请输入您的年龄:");
        int age = scanner.nextInt();
        System.out.println("请输入您的注册时间:");
        String resignDate = scanner.next();
        User user = new User(nick, pwd, age, sex, resignDate, degree);
        user.showMessage();
    }
}

结果图: