Java 练习题

1.设计一个方法，输入三个数字并输出最大整数

 

 import java.util.Scanner;
 ​
 public class Demo01MaxNumber {
     public static void main(String[] args) {
         Scanner sc = new Scanner(System.in);
         System.out.print("请输入三个整数：");
         int a = sc.nextInt();
         int b = sc.nextInt();
         int c = sc.nextInt();
         int maxNumber = maxNum(a,b,c);
         System.out.println("其中最大的数字为");
         System.out.print(maxNumber);
     }
     public static int maxNum(int one,int two,int three){
         // 单独判断
        /* if (one >= two && one >= three)
             return  one;
         else if (two >= three)
             return two;
         else
             return three;*/
         // 连续判断
        /* int max = 0;
         if (one > two)
             max = one;
         else
             max = two;
         if (max > three)
             return max;
         else
             return three;*/
         // 连续判断转化为三元
         /*int max = one > two ? one:two;
         max = max > three ? max:three;
         return max;*/
         // 另一种
         int max = one;
         if (two > max)
             max = two;
         if (three > max)
             max = three;
         return max;
     }
 }

 

2.设计一个程序，输入月份和年份，打印出此年月的天数

 

import java.util.Scanner;

public class Demo02YearMontheDate {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("请输入年份");
        int year = sc.nextInt();
        System.out.print("请输入月份");
        int month = sc.nextInt();
        System.out.println(year+"年"+month+"月，有"+isDay(year,month)+"天");
    }
    public static int isDay(int year,int month){
        int currentDays = 0;
        // 数组 写法  与 if else 写法 大同小异
        /*int[] runDays = {31,29,31,30,31,30,31,30,31,31,30,31};
        int[] pingDays = {31,28,31,30,31,30,31,30,31,31,30,31};
        // 判断 是否是闰年 ，若为闰年则天数加一天
        if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0){
            //计算 i从零开始，下标小于你输入的月份，在数组取出此月天数   也可用为 i < month
            for (int i = 0; i <= month - 1; i++)
                currentDays=runDays[i];
        }else {
            for (int i = 0; i <= month - 1; i++)
                currentDays=pingDays[i];
        }
        return currentDays;*/
        // switch 写法
        switch (month){
            case 1: case 3: case 5:case 7:case 9: case 10:case 12:
                currentDays = 31;
                break;
            case 4: case 6: case 8:case 11:
                currentDays = 30;
                break;
            case 2:
                if(year%4==0&&year%100!=0||year%400==0)
                    currentDays = 29;
                else
                    currentDays = 28;
                break;42         }
        return currentDays;
    }
}

 3.输入的非零三位数字依次输出该数字的百位和十位数，个位数。

 

//输入的非零三位数字依次输出该数字的百位和十位数，个位数

import java.util.Scanner;

public class Demo02Digital {
    public static void main(String[] args) {
        System.out.print("请输入一个三位数的整数：");
        int number = new Scanner(System.in).nextInt();
        digitalNum(number);
    }
    public static void digitalNum(int num){
        if (num > 0 ){
            int ge = num % 10;
            int shi = (num / 10) % 10;
            int bai = num / 100;
            System.out.print("个位数是"+ge+"，十位数是"+shi+"，百位数是"+bai+"。\n");
        }else {
            int ge = num % 10;
            int shi = (num / 10) % 10;
            int bai = num / 100;
            System.out.format("个位数是%d，十位数是%d，百位数是%d。\n",-ge,-shi,-bai);
        }

    }
}

 4.使用面向对象程序设计思想编写一个bankAccount类，该类具有属性：卡号，余额，持卡人姓名，密码。依据属性特征，设置相关属性的类型及访问权限；在类中提供构造方法完成对象的初始化并提供三个行为：显示余额，取款，存款。

 

import java.util.Random;


// 使用面向对象程序设计思想编写一个bankAccount类，该类具有属性：卡号，余额，持卡人姓名，密码。
// 依据属性特征，设置相关属性的类型及访问权限；
// 在类中提供构造方法完成对象的初始化并提供三个行为：显示余额，取款，存款。
public class BankAccount {
    // fields
    private String card;
    private double balance;
    private String name;
    private String password;

    // methods
    // 自动生成卡号
    public void setCard(){
        Random ran = new Random();
        String idCard="";
        for (int i = 0; i < 9; i++) {
            int a =ran.nextInt(16);
            idCard=idCard + a;
        }
        card = idCard;
    }
    // 获取卡号
    public String  getCard(){
        return card;
    }
    // 设置余额
    public void setBalance(double a){
        if (a > 0)
            balance = a;
    }
    // 获取余额 显示余额
    public double  getBalance(){
        return balance;
    }
    // 设置姓名
    public void setName(String a){
        name = a;
    }
    // 获取姓名
    public String  getName(){
        return name;
    }
    // 设置密码
    public void setPassword(String a){
        password = a;
    }
    // 获取密码
    public String  getPassword(){
        return password;
    }
    // 修改密码
    public boolean changePassword(String a){
        if (a.length()>0)
            password = a;
            return true;
    }
    // 存款
    public boolean increaseBalance(double a){
        if (a>0){
            balance += a;
            return true;
        }
          return false;
    }
    // 取款
    public boolean decreaseBalance(double a){
        if (a>0 && balance > a){
            balance -= a;
            return true;
        }
        return false;
    }
}

 

测试：

 

public class Demo08BankAccount {
    public static void main(String[] args) {
        BankAccount a = new BankAccount();
        a.setCard();
        System.out.println(a.getCard());
        a.setName("大嘟嘟");
        a.setBalance(89533.2);
        a.setPassword("123456789");
        System.out.println("持卡人姓名："+a.getName()+"\n卡号："+a.getCard()+"\n余额："+a.getBalance()+"\n密码："+a.getPassword());
        a.changePassword("");
        System.out.println("修改后的密码："+a.getPassword());
        a.increaseBalance(0.8);
        System.out.println("充值后的余额："+a.getBalance());
        a.decreaseBalance(800000);
        System.out.println("花费后的余额："+a.getBalance());
    }
}