package day01;
//三目运算
public class Test01 {
    public static void main(String[] args) {
        int a = -3;
        String r = a>0?"正数":(a == 0?"0":"负数");
        System.out.println(r);//结果为负数
    }
}

package day03;
//运算符的演示
public class OperDemo {
    public static void main(String[] args) {
        /*
         * 6.三目/条件运算符:
         *   1)语法:
         *       boolean?数1:数2
         *   2)执行过程:
         *       计算boolean的值:
         *         若为true，则整个表达式的结果为数1
         *         若为false，则整个表达式的结果为数2
         */
        /*
        int a=55,b=8;
        int max = a>b?a:b;
        System.out.println("max="+max);
        */
        
        /*
         * 5.字符串连接运算符:
         *   1)+:
         *     1.1)若两边都是数字，则做加法运算
         *     1.2)若两边出现字符串，则做字符串连接
         */
        /*
        System.out.println(100+200+""+300); //"300300"       
        System.out.println(100+200+300+""); //"600"
        System.out.println(""+100+200+300); //"100200300"
        
        int age = 37;
        System.out.println("age="); //age=
        System.out.println(age);    //37
        System.out.println("age="+age);
        System.out.println("我的年龄是:"+age);
        System.out.println("我今年"+age+"岁了");
        */
        
        /*
         * 4.赋值运算符:
         *   1)简单赋值运算符:=
         *   2)扩展赋值运算符:+=,-=,*=,/=,%=
         */
        /*
        int a = 5;
        a += 10; //相当于a=a+10
        System.out.println(a); //15
        a *= 2; //相当于a=a*2
        System.out.println(a); //30
        a /= 6; //相当于a=a/6
        System.out.println(a); //5
        */
        
        /*
         * 3.逻辑运算符:
         *   1)&&:短路与(并且)，两边都为真则为真，见false则false
         *        若第1个数为false则发生短路(后面的不执行了)
         *     ||:短路或(或者)，有一边为真则为真，见true则true
         *        若第1个数为true则发生短路(后面的不执行了)
         *      !:逻辑非(取反)，非真则假，非假则真
         *   2)逻辑运算是建立在关系运算的基础之上的，
         *     逻辑运算的结果也是boolean型
         */
        
        /*
        int a=5,b=10,c=5;
        boolean b5 = a<b || c++>2;
        System.out.println(b5); //true
        System.out.println(c);  //5，发生短路了
        
        boolean b4 = a>b && c++>2;
        System.out.println(b4); //false
        System.out.println(c);  //5，发生短路了
        */
        
        /*
        boolean b3 = !(a>b);
        System.out.println(b3);     //!false=true
        System.out.println(!(a<b)); //!true=false
        
        System.out.println(a>=b || c<b); //false||true=true
        System.out.println(c<=b || a>b); //true||false=true
        System.out.println(a!=b || b>c); //true||true=true
        System.out.println(b==c || c>b); //false||false=false
        
        boolean b2 = a>=b && c<b;
        System.out.println(b2);          //false&&true=false
        System.out.println(c<=b && a>b); //true&&false=false
        System.out.println(b==c && c>b); //false&&false=false
        System.out.println(a!=b && b>c); //true&&true=true
        */
        
        /*
         * 2.关系运算符:
         *   1)>(大于),<(小于)
         *     >=(大于或等于),<=(小于或等于)
         *     ==(等于),!=(不等于)
         *   2)关系运算的结果为boolean型，
         *     关系成立则为true，关系不成立则为false
         */
        /*
        int a=5,b=10,c=5;
        boolean b1 = a>b;
        System.out.println(b1);   //false
        System.out.println(c<b);  //true
        System.out.println(b>=a); //true
        System.out.println(c<=a); //true
        System.out.println(a==c); //true
        System.out.println(a!=c); //false
        */
        
        /*
         * 1.算术运算符:+,-,*,/,%,++,--
         *   1)%:取模/取余，余数为0即为整除
         *   2)++/--:自增1/自减1，可在变量前也可在变量后
         *     2.1)单独使用时，在前在后无差别
         *     2.2)被使用时，在前在后有差别:
         *           a++的值为a
         *           ++a的值为a+1
         */
        /*
        int a=5,b=5;
        //1)输出a--的值5  2)a自减1变为4
        System.out.println(a--); //5
        System.out.println(a);   //4
        //1)输出--b的值4  2)b自减1变为4
        System.out.println(--b); //4
        System.out.println(b);   //4
        */
        
        /*
        int a=5,b=5;
        int c=a++; //1)将a++的值5赋值给c  2)a自增1变为6
        int d=++b; //2)将++b的值6赋值给d  2)b自增1变为6
        System.out.println(a); //6
        System.out.println(b); //6
        System.out.println(c); //5
        System.out.println(d); //6
        */
        
        /*
        int a=5,b=5;
        a++; //相当于a=a+1
        ++b; //相当于b=b+1
        System.out.println(a); //6
        System.out.println(b); //6
        */
        
        /*
        System.out.println(5%2); //1，商2余1
        System.out.println(6%2); //0，商3余0--整除
        System.out.println(2%6); //2，商0余2
        System.out.println(8.675%2); //0.675
        */
    }
}

package day03;
//分支结构的练习
public class IfDemo {
    public static void main(String[] args) {
        int num = 4;
        switch(num){ //byte,short,char,int
        case 1: //if(num==1)
            System.out.println(111);
            break;
        case 2: //以此为入口
            System.out.println(222);
            break; //跳出switch
        case 3:
            System.out.println(333);
            break;
        default: //所有case都未匹配时执行
            System.out.println(666);
        }

package day03;
import java.util.Scanner;
//闰年的判断
public class LeapYear {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        System.out.println("请输入年份:");
        int year = scan.nextInt();
        
        boolean flag = (year%4==0 && year%100!=0) 
                       || 
                       year%400==0;
        String msg = flag ? year+"是闰年" : year+"不是闰年";
        System.out.println(msg);
    }
}

package day03;
import java.util.Scanner;
//成绩等级判断
public class ScoreLevel {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        System.out.println("请输入成绩:");
        int score = scan.nextInt();
        
        if(score<0 || score>100){
            System.out.println("成绩不合法");
        }else if(score>=90){ //score>=0 && score<=100  
            System.out.println("A-优秀");
        }else if(score>=80){
            System.out.println("B-良好");
        }else if(score>=60){
            System.out.println("C-中等");
        }else{
            System.out.println("D-不及格");
        }
        
    }
}


package day03;
import java.util.Scanner;
//年龄判断程序
public class AgeRange {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        System.out.println("请输入年龄:");
        int age = scan.nextInt();
        
        System.out.println(age>=18 && age<=50);
    }
}

package day03;
import java.util.Scanner;
//柜台收银程序
public class Cashier {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        System.out.println("请输入单价:");
        double unitPrice = scan.nextDouble();
        System.out.println("请输入数量:");
        double amount = scan.nextDouble();
        System.out.println("请输入金额:");
        double money = scan.nextDouble();
        
        //计算总价(单价*数量)
        double totalPrice = unitPrice*amount;
        if(totalPrice>=500){ //满500
            totalPrice*=0.8; //打8折
        }
        
        if(money>=totalPrice){ //够
            double change = money-totalPrice; //计算找零(给的钱-总价)
            System.out.println("总价为:"+totalPrice+"，找零为:"+change);
        }else{ //不够
            System.out.println("ERROR!钱不够");
        }
        
    }
}

package day03;
import java.util.Scanner;
//命令解析程序
public class CommandBySwitch {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        System.out.println("请选择功能: 1.显示全部记录  2.查询登录记录  0.退出");
        int command = scan.nextInt();
        
        switch(command){
        case 1:
            System.out.println("显示全部记录");
            break;
        case 2:
            System.out.println("查询登录记录");
            break;
        case 0:
            System.out.println("欢迎下次再来");
            break;
        default:
            System.out.println("输入错误");
        }
        
    }
}