3.24·Java基础学习

目录

类与对象

1.单个对象建立的内存图

2.成员变量和局部变量的区别

3.this关键字

4.this的内存图

 5.权限修饰符​编辑

6.对私有权限内容赋值

总​​​​​​​结

一个项目：电影

movie.java

MovieService.java 

test.java

Java的API使用

Java : String

String面试题来啦～

String内容比较wow

String的遍历方法wow

String的截取

String的替换

类与对象

1.单个对象建立的内存图

2.成员变量和局部变量的区别

3.this关键字

4.this的内存图

 5.权限修饰符

6.对私有权限内容赋值

​​​​​​​

总​​​​​​​结

一个项目：电影

movie.java

package movie;public class movie {private int id;private String title;private String time;private double score;private String area;private String type;private String director;private String starring;// public movie() {// }public movie(int id, String title, String time, double score, String area, String type, String director, String starring) {this.id = id;this.title = title;this.time = time;this.score = score;this.area = area;this.type = type;this.director = director;this.starring = starring;}public int getId() {return this.id;}public void setId(int id) {this.id = id;}public String getTitle() {return this.title;}public void setTitle(String title) {this.title = title;}public String getTime() {return this.time;}public void setTime(String time) {this.time = time;}public double getScore() {return this.score;}public void setScore(double score) {this.score = score;}public String getArea() {return this.area;}public void setArea(String area) {this.area = area;}public String getType() {return this.type;}public void setType(String type) {this.type = type;}public String getDirector() {return this.director;}public void setDirector(String director) {this.director = director;}public String getStarring() {return this.starring;}public void setStarring(String starring) {this.starring = starring;}}

MovieService.java 

package movie;import java.util.Scanner;import movie.movie;public class MovieService {movie[] movies;Scanner sc = new Scanner(System.in);public MovieService(movie[] movies){this.movies = movies;}public void start(){System.out.println("----------电影信息系统----------");lo:while(true){System.out.println("请输入你的选择哦");System.out.println("1、查询电影全部信息");System.out.println("2、根据id查询电影信息");System.out.println("3、退出");int choice = sc.nextInt();switch(choice){case 1:AllMessage();break;case 2:SearchMovie();break;case 3:System.out.println("谢谢你的使用啦，再见哦");break lo;}System.out.println();}}private void SearchMovie() {System.out.println("请输入你要查找的id哦");int id = sc.nextInt();for (int i = 0; i < movies.length; i++) {if(movies[i].getId() == id){System.out.println(movies[i].getId()+" "+movies[i].getTitle()+" "+movies[i].getTime()+" "+movies[i].getScore()+" "+movies[i].getArea()+" "+movies[i].getType()+" "+movies[i].getDirector()+" "+movies[i].getStarring());return ;}}System.out.println("输入有误哦，检查后再来一遍咯");}private void AllMessage() {for (int i = 0; i < movies.length; i++) {System.out.println(movies[i].getTitle() + " " + movies[i].getScore());}}}

test.java

package movie;import movie.movie;public class test {public static void main(String[] args) {movie m1 = new movie(1, "东八区的先生们", "2022", 2.1, "中国大陆", "喜剧", "夏睿", "张𨌺 𡈼𣇈展");movie m2 = new movie(2, "上海堡垒", "2019", 2.9, "中国大陆", "爱情", "滕华涛", "鹿晗 舒淇");movie m3 = new movie(3, "纯洁心灵", "2015", 2.2, "", "中国大陆", "毕志飞", "朱一文 李彥漫");movie[] movies = {m1, m2, m3};MovieService movieService = new MovieService(movies);movieService.start();}
}

Java的API使用

next()->碰到空格和Tab键就终止

nextLine()->一串都下来

Java : String

String s1 = "abc";
String s2 = "abc";
System.out.println(s1 == s2);
// True

 当我们使用双引号创建字符串对象时，会检查常量池里面是否存在该数据

不存在的话：创建        存在的话：复用->最后都指向同一个地址哦

String面试题来啦～

ps：第四个系统调用了“Java优化机制” 

String内容比较wow

import java.util.Scanner;public class A{public static void main(String[] args) {String name = "A宝";String password = "040502";Scanner sc = new Scanner(System.in);for(int i = 1 ; i <= 3 ; i++){System.out.println("请输入用户名");String InputName = sc.nextLine();System.out.println("请输入密码哦");String InputPassword = sc.nextLine();// equal是要考虑大小写的。equalIgnoreCase是没有考虑大小写哦if(InputName.equals(name) && InputPassword.equals(password)){System.out.println("登入成功wow!");break;}else{if(i == 3){System.out.println("三次机会用完啦，明天再来吧！");}else{System.out.println("登入错误，还有"+(3-i) +"次机会");}}}}
}

String的遍历方法wow

public class A{public static void main(String[] args) {// String的第一种遍历方式（效率更高）String s = "wlc";char[] s1 = s.toCharArray();for (int i = 0; i < s1.length; i++) {System.out.print(s1[i]+ " ");}System.out.println();// String的第二种遍历方式for(int i = 0 ; i < s.length() ; i++){System.out.print(s.charAt(i)+ " ");}System.out.println();}
}

String的截取

import java.util.Scanner;public class A {public static void main(String[] args) {Scanner sc = new Scanner(System.in);System.out.println("请输入手机号呀");String tel = sc.nextLine();String start = tel.substring(0, 3);String end = tel.substring(7);System.out.println(start + "****" + end);}
}

String的替换

import java.util.Scanner;public class A {public static void main(String[] args) {Scanner sc = new Scanner(System.in);System.out.println("请输入一串字符串");String s = sc.nextLine();String result = s.replace("wlc", "WLC");System.out.println(result);}
}