java学习笔记06-面向对象学习
java学习笔记06
记录下面向对象的学习
类的定义
public class Phone {
// 成员变量
String brand;
int price;
// 成员方法
public void call() {
System.out.println("打电话");
}
public void sendMsg() {
System.out.println("发短信");
}
}
对象的创建使用
创建对象
创建对象格式：
类名 对象名 = new 类名();
Phone p = new Phone();
使用对象
使用成员变量：
对象名.变量名
p.brand
使用成员方法：
对象名.方法名
p.call()
例如：
public class PhoneDemo {
public static void main(String[] args) {
Phone p = new Phone();
System.out.println(p.brand);
System.out.println(p.price);
p.brand = "小米";
p.price = 3999;
System.out.println(p.brand);
System.out.println(p.price);
p.call();
}
}
private和this
public class Student {
private String name;
private int age;
public void setName(String name) {
this.name = name;
}
public String getName() {
return name;
}
public void setAge(int age) {
this.age = age;
}
public int getAge() {
return age;
}
public void show() {
System.out.println(this.name + "," + this.age);
}
}
实例化类使用
public class StudentTest {
public static void main(String[] args) {
Student s1 = new Student();
s1.setName("后羿");
s1.setAge(100);
s1.show();
}
}
构造方法
构造方法是和类名相同的成员方法，构造方法支持重载
格式为：
修饰符 类名 () {}
public class Student {
private String name;
private int age;
public Student () {
}
public Student (String name, int age) {
this.name = name;
this.age = age;
}
public void setName(String name) {
this.name = name;
}
public String getName() {
return name;
}
public void setAge(int age) {
this.age = age;
}
public int getAge() {
return age;
}
public void show() {
System.out.println(this.name + "," + this.age);
}
}
实例化类
public class StudentTest {
public static void main(String[] args) {
Student s1 = new Student();
s1.setName("后羿");
s1.setAge(100);
s1.show();
Student s2 = new Student("张良", 40);
s2.show();
}
}
标准类的制作
1、成员变量
使用private修饰
2、构造方法
提供一个无参构造方法
提供有个带多个参数的构造方法
3、成员方法
提供每一个成员变量对应的setXxx()/getXxx()
提供一个显示对象信息的show()
4、创建对象并为其成员变量赋值的两种方式
无参构造方法创建对象后使用setXxx()赋值
使用带参构造方法直接创建带有属性值的对象
IDEA 类方法定义时快捷键ALT+INSERT
面向对象练习题
实现一个学生管理系统
Student.java
package study.com;
public class Student {
private String sid;
private String name;
private String age;
private String location;
public Student () {
}
public Student (String sid, String name, String age, String location) {
this.sid = sid;
this.name = name;
this.age = age;
this.location = location;
}
public void setSid(String sid) {
this.sid = sid;
}
public void setName(String name) {
this.name = name;
}
public void setAge(String age) {
this.age = age;
}
public void setLocation(String location) {
this.location = location;
}
public String getSid() {
return sid;
}
public String getName() {
return name;
}
public String getAge() {
return age;
}
public String getLocation() {
return location;
}
public void show() {
System.out.println("学号:" + this.sid + "\t" + "姓名:" + this.name + "\t" + "年龄:" + this.age + "\t" + "地址:" + this.location);
}
}
StudentManage.java
package study.com;
import java.util.ArrayList;
import java.util.Scanner;
import java.util.TreeMap;
public class StudentManage {
public static void main(String[] args) {
ArrayList<Student> stuList = new ArrayList<Student>();
while (true) {
System.out.println("----欢迎进入学生管理系统----");
System.out.println("1 添加学生");
System.out.println("2 删除学生");
System.out.println("3 修改学生");
System.out.println("4 查看所有学生");
System.out.println("5 退出");
System.out.println("请输入你的选择: ");
Scanner sc = new Scanner(System.in);
String choose = sc.nextLine();
switch (choose) {
case "1":
addStudent(stuList);
break;
case "2":
delStudent(stuList);
break;
case "3":
editStudent(stuList);
break;
case "4":
findAllStudent(stuList);
break;
case "5":
System.exit(0);
break;
default:
System.out.println("错误的指令，请重新输入！");
}
}
}
public static void addStudent(ArrayList<Student> arrL) {
Scanner sc = new Scanner(System.in);
String sid;
while (true) {
System.out.println("请输入学生学号:");
sid = sc.nextLine();
if (sidIsUsed(arrL, sid)) {
System.out.println("学号已存在,不可重复添加,请重新输入");
continue;
} else {
break;
}
}
System.out.println("请输入学生姓名:");
String name = sc.nextLine();
System.out.println("请输入学生年龄:");
String age = sc.nextLine();
System.out.println("请输入学生地址:");
String location = sc.nextLine();
Student student = new Student(sid, name, age, location);
arrL.add(student);
System.out.println("添加学生成功！");
}
public static void delStudent(ArrayList<Student> arrL) {
System.out.println("请输入要删除的学生的学号: ");
Scanner sc = new Scanner(System.in);
String sid = sc.nextLine();
boolean deleteStatus = false;
for (int i=0; i<arrL.size(); i++) {
Student stu = arrL.get(i);
if (stu.getSid().equals(sid)) {
arrL.remove(i);
deleteStatus = true;
break;
}
}
if (!deleteStatus) {
System.out.println("输入学号的学生不存在");
} else {
System.out.println("删除成功");
}
}
public static void findAllStudent(ArrayList<Student> arrL) {
int ln = arrL.size();
if (ln == 0) {
System.out.println("无信息，请添加信息后再查看");
return;
}
for (int i=0; i<ln; i++) {
Student stu = arrL.get(i);
stu.show();
}
}
public static void editStudent(ArrayList<Student> arrL) {
System.out.println("请输入要编辑的学生的学号: ");
Scanner sc = new Scanner(System.in);
String sid = sc.nextLine();
boolean editStatus = false;
Student tmp = null;
for (int i=0; i<arrL.size(); i++) {
Student stu = arrL.get(i);
if (stu.getSid().equals(sid)) {
editStatus = true;
tmp = stu;
break;
}
}
if (!editStatus) {
System.out.println("输入学号的学生不存在");
} else {
System.out.println("请输入学生姓名:");
String name = sc.nextLine();
System.out.println("请输入学生年龄:");
String age = sc.nextLine();
System.out.println("请输入学生地址:");
String location = sc.nextLine();
System.out.println("删除成功");
tmp.setName(name);
tmp.setAge(age);
tmp.setLocation(location);
System.out.println("修改学生信息成功");
}
}
public static boolean sidIsUsed(ArrayList<Student> arrL, String sid) {
boolean existFlag = false;
for (int i=0; i<arrL.size(); i++) {
Student stu = arrL.get(i);
if (stu.getSid().equals(sid)) {
existFlag = true;
break;
}
}
return existFlag;
}
}
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