方法

 

package com.unit4.test;

public class Test1 {
    
    //返回修饰符public:项目中任何地方都可以调用
    //返回值类型void:无返回值
    //方法名function1:驼峰命名
    //()中写参数列表，可以省略
    //static静态方法：可以在本类中直接调用
    public static void function1(){
        //方法体
        System.out.println("这是一个方法！");
    }

    public static void main(String[] args) {
        System.out.println("main方法被执行了！");
        
        //调用方法
        function1();
        
    }

}

 

package com.unit4.test;

public class Test2 {
    //参数列表和返回值
    
    //传入单个参数
    public static void function1(int num) {
        System.out.println("传参");
        System.out.println("数字是:"+num);
    }
    
    //传入多个参数
    public static void function2(String name,int num,String level) {
        double total=num*(1+0.3);
        System.out.println(level+"用户"+name+",您好，您的余额为："+total);
    }
    
    //传入不定长参数
    public static void function3(int[] scores) {
        int sum=0;
        for(int x:scores) {
            sum+=x;
        }
        double avg=sum*1.0/scores.length;
        System.out.println(avg);
    }
    
    //返回值
    public static double function4(int[] scores) {
        int sum=0;
        for(int x:scores) {
            sum+=x;
        }
        double avg=sum*1.0/scores.length;
//        System.out.println(avg);
        return avg;  //将avg作为返回值传递到方法外面
    }
    
    public static String function5(String fruit) {
        System.out.println("榨汁机工作中");
        String aa=fruit+"汁";
        return aa;
    }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        //function1(10);
//        function2("张三",10000,"钻石");
        
        int[] ss= {66,77,56,90,84};
//        function3(ss);
        
//        double avg=function4(ss);
//        System.out.println(avg);
        
        String aa=function5("葡萄");
        System.out.println(aa);

    }

}

 

package com.unit4.test;

public class Test3 {
    public static void f1() {
        System.out.println("f1");
    }
    
    public static void f2() {
        System.out.println("f2");
    }
    
    public static void f3() {
        f1();
        f2();
    }
    
    //递归
    public static int sum(int i,int result) {
//        System.out.println(i);
        result+=i;
        i++;
        if(i<=100) {
            result=sum(i,result);
        }
        return result;
    }

    public static void main(String[] args) {
//        f3();
        int re=sum(0,0);
        System.out.println(re);

    }

}

 

package com.unit4.test;

public class Test4 {
    // 练习一：体积计算器
    public static double getVol(double r,double h) {
        double vol=3.1415926*r*r*h;
        return vol;
    }
    
    //练习二：修改密码
    public static String changePwd(String oldpwd,String newpwd) {
        String pwd="123456";
        String msg="错误";
        if(oldpwd.equals(pwd)) {
            if(newpwd.length()<6) {
                System.out.println("请输入大于6位数的密码");
            }else {
                pwd=newpwd;
                msg="正确";
                System.out.println("密码输入正确");
            }
        }else {
            System.out.println("旧密码输入错误");
        }
        return msg;
    }

    public static void main(String[] args) {
//        double vol=getVol(2, 5);
//        System.out.println(vol);
        
        String msg=changePwd("123456", "1239288");
        System.out.println(msg);
        

    }

}

 

package com.unit4.test;

public class Test5 {
    // 变量作用域范围
    
    //定义在类中的变量作用范围是整个类
    static String a="定义在类中的变量";
            
    public static void f1() {
        //定义在方法内部的变量，作用范围也只在方法内部，外部无法访问
//        String a1="定义在f1中的变量";
//        System.out.println(a1);
        
        String a="xxxx";
        System.out.println("f1"+a);
    }
    
    public static void f2() {
        System.out.println("f2"+a);
    }
    
    public static void f3() {
        System.out.println("f3"+a);
    }

    public static void main(String[] args) {
        String a1="main变量";
        System.out.println(a1);
        
        f1();
        f2();
        f3();
        

    }

}

 

package com.unit4.test;

import java.util.Scanner;

public class Test6 {
    //例：迷你图书借阅系统
    static String[] nameArray= {"java教程","python入门","C语言教程","ps大神之路"};//书名
    static String[] authorArray= {"张三","李四","王五","赵柳"};//作者
    static int[] stateArray= {1,1,2,2};//状态：1.可借  2.不可借
    static int[] borrowCount= {67,70,43,15};//累计借出次数
    static Scanner s=new Scanner(System.in);
    
    //归还图书
    public static void returnBook() {
        System.out.println("请输入书名：");
        String bookname4=s.next();
        String msg="图书不存在！";
        double rent=0;
        for(int i=0;i<nameArray.length;i++) {
            if(bookname4.equals(nameArray[i])) {
                if(stateArray[i]==2) {
                    System.out.println("请输入租借天数：");
                    int days=s.nextInt();
                    if(days>31 || days<1) {
                        System.out.println("输入错误！");
                        msg="归还失败！";
                    }else {
                        msg="图书已还！";
                        stateArray[i]=1;
                        rent=2.0*days;
                        System.out.println(bookname4+"归还成功！租金："+rent+"元");
                    }
                }else{
                    msg="输入错误，图书未被借出！";
                }
            }
        }
        if("图书已还！".equals(msg)) {
            showBooks(nameArray,authorArray,stateArray,borrowCount);
        }else {
            System.out.println(msg);
        }
    }
    
    //借出图书
    public static void borrowBook() {
        System.out.println("请输入书名：");
        String bookname3=s.next();
        String msg="图书不存在！";
        for(int i=0;i<nameArray.length;i++) {
            if(bookname3.equals(nameArray[i])) {
                if(stateArray[i]==2) {
                    msg="抱歉！图书已被借出！";
                }else {
                    msg="图书可借！";
                    stateArray[i]=2;
                    borrowCount[i]+=1;
                }
            }
        }
        if("图书可借！".equals(msg)) {
            System.out.println(bookname3+"借出成功！");
            showBooks(nameArray,authorArray,stateArray,borrowCount);
        }else {
            System.out.println(msg);
        }
        
    }
    
    //删除图书
    public static void delBook() {
        System.out.println("请输入书名：");
        String bookname1=s.next();
        int msg2=1;
        int index=0;
        for(int i=0;i<nameArray.length;i++) {
            if(bookname1.equals(nameArray[i])) {
                msg2=2;
                index=i;
            }
        }
        if(msg2==2) {
            String[] nameArray2=new String[nameArray.length-1];
            String[] authorArray2=new String[nameArray.length-1];
            int[] stateArray2=new int[nameArray.length-1];
            int[] borrowCount2=new int[nameArray.length-1];
            
            for(int i=0;i<nameArray2.length;i++) {
                if(i<index) {
                    nameArray2[i]=nameArray[i];
                    authorArray2[i]=authorArray[i];
                    stateArray2[i]=stateArray[i];
                    borrowCount2[i]=borrowCount[i];
                }else if(i>=index) {
                    nameArray2[i]=nameArray[i+1];
                    authorArray2[i]=authorArray[i+1];
                    stateArray2[i]=stateArray[i+1];
                    borrowCount2[i]=borrowCount[i]+1;
                }
            }
            System.out.println("删除成功！添加书名："+bookname1);
            showBooks(nameArray2,authorArray2,stateArray2,borrowCount2);
        }else {
            System.out.println("图书不存在！");
        }
    }
    
    //增加图书
    public static void addBook() {
        if(nameArray.length>6) {
            System.out.println("书架已满！");
        }else {
            System.out.println("请输入书名：");
            String bookname=s.next();
            System.out.println("请输入作者名：");
            String author=s.next();
            int msg1=1;
            for(String n:nameArray) {
                if(bookname.equals(n)) {
                    msg1=2;
                }
            }
            if(msg1==2) {
                System.out.println("该图书已存在！");
            }else {
                String[] nameArray1=new String[nameArray.length+1];
                String[] authorArray1=new String[nameArray.length+1];
                int[] stateArray1=new int[nameArray.length+1];
                int[] borrowCount1=new int[nameArray.length+1];
                
                for(int i=0;i<nameArray.length;i++) {
                    nameArray1[i]=nameArray[i];
                    authorArray1[i]=authorArray[i];
                    stateArray1[i]=stateArray[i];
                    borrowCount1[i]=borrowCount[i];
                }
                nameArray1[nameArray1.length-1]=bookname;
                authorArray1[authorArray1.length-1]=author;
                stateArray1[stateArray1.length-1]=1;
                borrowCount1[borrowCount1.length-1]=0;
                
                System.out.println("添加成功！添加书名："+bookname);
                showBooks(nameArray1,authorArray1,stateArray1,borrowCount1);
            }
        }
            
    }
    
    //展示图书
    public static void showBooks(String a[],String b[],int c[],int d[]) {
        System.out.println("书名---作者---状态---累计借出次数");
        for(int i=0;i<a.length;i++) {
            String status="可借";
            if(c[i]==2) {
                status="不可借";
            }
            System.out.println(a[i]+"---"+b[i]+"---"+status+"---"+d[i]);
        }
    }
    
    //登录
    public static String login() {
        System.out.println("请输入用户名：");
        String name=s.next();
        System.out.println("请输入密码：");
        String pwd=s.next();
        String msg="错误";
        
        if("aaa".equals(name) && "123".equals(pwd)) {
            msg="正确";
        }
        return msg;
    }
    
    //显示主菜单
    public static void showMenu() {
        System.out.println("--------------主菜单---------------------");
        System.out.println("1.查看所有图书");
        System.out.println("2.增加图书");
        System.out.println("3.删除图书");
        System.out.println("4.借出图书");
        System.out.println("5.归还图书");
        System.out.println("6.退出");
        System.out.println("请选择菜单编号：");
    }

    public static void main(String[] args) {

        while(true) {
            String msg=login();
            if("错误".equals(msg)) {
                continue;
            }else if("正确".equals(msg)) {
                while(true) {
                    System.out.println("欢迎来到图书管理系统！");
                    showMenu();
                    int choice=s.nextInt();
                    if(choice==1) {
                        showBooks(nameArray,authorArray,stateArray,borrowCount);
                    }else if(choice==2) {
                        addBook();
                    }else if(choice==3) {
                        delBook();
                    }else if(choice==4) {
                        borrowBook();
                    }else if(choice==5) {
                        returnBook();
                    }else if(choice==6) {
                        continue;
                    }
                }
                
            }
        }

    }

}