（一)Java的变量

1.1 成员变量和局部变量的区别

• 1、类中位置不同:成员变量(类中，方法外)、局部变量(常见于方法中)
• 2、初始化值不同:成员变量(有默认值，不需要初始化赋值)，局部变量(没有默认值，使用之前必须完成赋值)
• 3、内存位置不同:成员变量(存在于堆内存)，局部变量(内存)
• 4、作用域不同: 成员变量(整个对象)，局部变量(在所归属的大括号中)
• 5、生命周期不同:成员变量(与对象同生共死)，局部变量(方法调用而生，方法结束而亡)

1.2 成员变量

成员变量在类的里面，但是在方法外面

public class Test2 {
    String name; //成员变量
    double score;
    public void svg(){ //方法
        
    }
}

1.3 局部变量

局部变量是在方法内部定义的

public class Test2 {
    String name; //成员变量
    double score;
    public void svg(){ //方法
        int b = 20; //局部变量
    }
}

1.4 实体类的案例

面向对象综合案例-模仿电影信息系统
需求

• 展示系统中的全部电影(每部电影展示:名称、价格)。
• 允许用户根据电影编号(id)查询出某个电影的详细信息

设计一个电影类 也是实体类

package com.qianxin.dainying;

public class Movie {
    private int id;
    private String name;
    private double price;
    private double score;
    private String director;
    private String actor;
    private String info;

    public Movie() {
    }

    public Movie(int id, String name, double price, double score, String director, String actor, String info) {
        this.id = id;
        this.name = name;
        this.price = price;
        this.score = score;
        this.director = director;
        this.actor = actor;
        this.info = info;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public double getScore() {
        return score;
    }

    public void setScore(double score) {
        this.score = score;
    }

    public String getDirector() {
        return director;
    }

    public void setDirector(String director) {
        this.director = director;
    }

    public String getActor() {
        return actor;
    }

    public void setActor(String actor) {
        this.actor = actor;
    }

    public String getInfo() {
        return info;
    }

    public void setInfo(String info) {
        this.info = info;
    }
}

设计一个电影操作类

package com.qianxin.dainying;

public class MovieOperator {
    private Movie[] movies;
    public MovieOperator(Movie[] movies){
        this.movies = movies;
    }
    /** 1、展示系统全部电影信息 movies =[m1，m2，m3,...]*/
    public void printAllMovies() {
        System.out.println("-----系统全部电影信息如下:");
        for (int i = 0; i < movies.length; i++) {
            Movie m = movies[i];
            System.out.println("编号:"+ m.getId());
            System.out.println("名称:"+ m.getName());
            System.out.println("价格:"+ m.getPrice());
            System.out.println("----------------");
        }
    }
    public void searchMoiveById(int id) {
        for (int i = 0; i < movies.length; i++) {
            Movie m = movies[i];
            if (m.getId() == id) {
                System.out.println("该电影详情如下:");
                System.out.println("编号:" + m.getId());
                System.out.println("名称:" + m.getName());
                System.out.println("价格::" + m.getPrice());
                System.out.println("得分:" + m.getScore());
                System.out.println("导演:" + m.getDirector());
                System.out.println("主演:" + m.getActor());
                System.out.println("其他信息:" + m.getInfo());
                return;
            }
        }
        System.out.println("没有该电影信息~");
    }
}

设计主程序

package com.qianxin.dainying;

import java.util.Scanner;

public class Test {
    public static void main(String[] args) {
        Movie[] movies = new Movie[4];
        movies[0] =new Movie( 1,"水门桥",38.9,9.8,"徐克","吴京","12万人想看");
        movies[1]= new Movie( 2,"出拳吧",39,7.8,"唐晓白","田雨","3.5万人想看");
        movies[2]= new Movie( 3,"月球陨落",42,7.9,"罗兰","贝瑞","17.9万人想看");
        movies[3]= new Movie( 4,"一点就到家",35, 8.7, "许宏字","刘吴然","10.8万人");

        // 4、创建一部电影操作类的对象，接收电影数据，并对其进行业务处理
        MovieOperator operator =new MovieOperator(movies);
        operator.printAllMovies();
        operator.searchMoiveById(3);
                    
        
        System.out.println("==电影信息系统==");
        System.out.println("1、查询全部电影信息");
        System.out.println("2、根据id查询某个电影的详细信息展示");
        System.out.println("请您输入操作命令:");
        Scanner sc=new Scanner(System.in);
        int command =sc.nextInt();
        switch(command) {
            case 1:
                // 展示全部电影信息
                operator.printAllMovies();
                break;
            case 2:
                // 根据id查询某部电影的详细信息展示
                System.out.println("请您输入查询的电影id:");
                int id = sc.nextInt();
                operator.searchMoiveById(id);
                break;
            default:
                System.out.println("您输入的命令有问题~~");
        }
    }
}