该文章Github地址：https://github.com/AntonyCheng/java-notes
在此介绍一下作者开源的SpringBoot项目初始化模板（Github仓库地址：https://github.com/AntonyCheng/spring-boot-init-template & CSDN文章地址：https://blog.csdn.net/AntonyCheng/article/details/136555245），该模板集成了最常见的开发组件，同时基于修改配置文件实现组件的装载，除了这些，模板中还有非常丰富的整合示例，同时单体架构也非常适合SpringBoot框架入门，如果觉得有意义或者有帮助，欢迎Star & Issues & PR！
上一章：由浅到深认识Java语言（25）：正则表达式
38.阶段性练习
练习一：
编写一个程序，用于接收用户输入的五个数，并计算这五个数的平均数，最后将计算结果返回；
import java.util.Scanner;public class Demo {public static void main(String[] args) {double[] arr = new double[5];double pjs = method(arr);System.out.println("你输入的五个数的平均数是："+pjs);}public static double method(double[] arr) {Scanner sc = new Scanner(System.in);double sum = 0;System.out.println("请输入五个数，用空格分开：");for (int i = 0; i < arr.length; i++) {arr[i] = sc.nextDouble();sum += arr[i];}sc.close();return sum/5;}
}
打印效果如下：
练习二：
编写一个函数，用于接收三角形的底和高，并计算该三角形的面积，将面积返回；
import java.util.Scanner;public class Demo {public static void main(String[] args) {Scanner sc = new Scanner(System.in);System.out.println("请输入你的三角形的底和高（用空格隔开）：");double floor = sc.nextDouble();double high = sc.nextDouble();sc.close();double area = method(floor,high);System.out.println("你的三角形面积是："+area);}public static double method(double floor,double high) {return (floor*high)/2;}
}
打印效果如下：
练习三：
编写一个函数，用于接收 3 到 10 之间的一个数，然后输出由星号组成的长方形；
例如：用户输入 4 ，输出结果如下：
****
* *
* *
****
import java.util.Scanner;public class Demo {public static void main(String[] args) {Scanner sc = new Scanner(System.in);System.out.println("请输入你的图像行数：");int num = sc.nextInt();sc.close();method(num);}public static void method(int n) {for (int i = 0; i < n; i++) {if (i == 0 || i == n-1) {for (int j = 0; j < n; j++) {System.out.print("*");}}else {for (int j = 0; j < n; j++) {if(j == 0||j==n-1) {System.out.print("*");}else {System.out.print(" ");}}}System.out.println();}}
}
打印效果如下：
练习四：
写一个方法 boolean checkIsOddNumber(int num) 判断输入是否为奇数；
import java.util.Scanner;public class Demo {public static void main(String[] args) {Scanner sc = new Scanner(System.in);System.out.println("请输入一个需要判断的数：");int num = sc.nextInt();boolean checkIsOddNumber = checkIsOddNumber(num);System.out.println(checkIsOddNumber);}public static boolean checkIsOddNumber(int num) {if (num % 2 == 0) {return false;} else {return true;}}
}
打印效果如下：
练习五：
写一个方法 boolean checkIsPrimeNumber(int num) 判断输入是否为素数；
方法一：
import java.util.Scanner;public class Demo {public static void main(String[] args) {Scanner sc = new Scanner(System.in);System.out.println("请输入一个需要判断的数：");int num = sc.nextInt();boolean checkIsPrimeNumber = checkIsPrimeNumber(num);System.out.println(checkIsPrimeNumber);}public static boolean checkIsPrimeNumber(int num) {if(num<=1) {return false;}else {int count = 0;for (int i = 2; i <= num; i++) {if(num%i != 0) {count++;}}if(count == num-2) {return true;}else {return false;}}}
}
方法二：
import java.util.Scanner;public class Demo {public static void main(String[] args) {Scanner sc = new Scanner(System.in);System.out.println("请输入一个需要判断的数：");int num = sc.nextInt();boolean checkIsPrimeNumber = checkIsPrimeNumber(num);System.out.println(checkIsPrimeNumber);}public static boolean checkIsPrimeNumber(int num) {if (num <= 1) {return false;} else {for (int i = 2; i < num; i++) {if (num % i == 0) {return false;}}}return true;}
}
打印效果如下：
练习六：
打印一棵圣诞树；
import java.util.Iterator;
import java.util.Scanner;public class Demo {public static void main(String[] args) {method();}public static void method() {for (int i = 1; i <= 15; i++) {if (i <= 5) {for (int j = 0; j < 8 - i; j++) {System.out.print(" ");}for (int j = 0; j < 2 * i - 1; j++) {System.out.print("*");}System.out.println();} else if (i <= 11) {for (int j = 0; j < 11-i; j++) {System.out.print(" ");}for (int j = 0; j < 2*i-7; j++) {System.out.print("*");}System.out.println();} else {for (int j = 0; j < 6; j++) {System.out.print(" ");}for (int j = 0; j < 3; j++) {System.out.print("*");}System.out.println();}}}
}
打印效果如下：
练习七：
用 Java 代码将数组元素顺序颠倒；
import java.util.Arrays;public class Demo {public static void main(String[] args) {int arr[] = {2,3,4,5,6,7};int[] method = method(arr);System.out.println(Arrays.toString(method));}public static int[] method(int[] arr) {int n = arr.length;for (int i = 0; i < arr.length/2; i++) {int temp = arr[i];n=n-1;arr[i] = arr[n];arr[n] = temp;}return arr;}
}
打印效果如下：
练习八：
写一个名为 Account 的类模拟账户，该类的属性和方法如下图所示：
该类包括的属性：账号 id ，余额 balance ， 年利率 annualInterestRate；
包含的方法：访问器方法（getter() 和 setter())，取款方法 withdraw() ，存款方法 deposit() ；
注意取款方法应该判断用户余额是否满足取款条件；
再写一个 Customer 的类模拟客户，该类的属性和方法如下图所示：
该类包括的属性：姓 firstName ，名 lastName 和账号 account；
声明一个公有构造器，这个构造器带有两个代表姓名的参数；
声明两个公有存取器来访问该对象的属性；
以上为基础，写一个测试程序：
-
创建一个Customer，名字叫 Xiao Wu ，他有一个账号为 1900，余额为2000，年利率为 1.23% 的账户。
-
对 Xiao Wu操作：
存入 100 元，再取出 960 元，再取出 2000 元，然后打印 Xiao Wu 的基本信息；
信息：存入成功！100.0元；取出成功！960.0元；余额不足取款失败；Customer [Xiao,Wu] has a account: id is 1900,annualInterestRate is 1.23%,balance is 1140.0;
package top.sharehome.Bag;public class Demo {public static void main(String[] args) {Customer c = new Customer("Xiao", "Wu", new Account(1900, 2000, 1.23));Account a = c.getAccount();a.deposit(100);a.withdraw(960);a.withdraw(2000);System.out.println(a.getBalance());String string = c.toString(a.getAnnualInterestRate(), a.getBalance(), a.getId());System.out.println(string);}
}class Account {private int id;private double balance;private double annualInterestRate;public Account() {super();// TODO Auto-generated constructor stub}public Account(int id, double balance, double annualInterestRate) {super();this.id = id;this.balance = balance;this.annualInterestRate = annualInterestRate;}public int getId() {return id;}public void setId(int id) {this.id = id;}public double getBalance() {return balance;}public void setBalance(double balance) {this.balance = balance;}public double getAnnualInterestRate() {return annualInterestRate;}public void setAnnualInterestRate(double annualInterestRate) {this.annualInterestRate = annualInterestRate;}public void withdraw(double amount) {if (amount > this.balance) {System.out.println("余额不足取款失败");} else {this.balance = this.balance - amount;System.out.println("取出成功！" + amount + "元");}}public void deposit(double amount) {this.balance += amount;System.out.println("存入成功！" + amount + "元");}
}class Customer {private String firstName;private String lastName;private Account account;public Customer(String firstName, String lastName, Account account) {super();this.firstName = firstName;this.lastName = lastName;this.account = account;}public Customer() {super();// TODO Auto-generated constructor stub}public String getFirstName() {return firstName;}public void setFirstName(String firstName) {this.firstName = firstName;}public String getLastName() {return lastName;}public void setLastName(String lastName) {this.lastName = lastName;}public Account getAccount() {return account;}public void setAccount(Account account) {this.account = account;}public String toString(double annualInterestRate, double balance, double id) {return "Customer [" + firstName + ", " + lastName + "] has a account: id is " + account.getId()+ " , annualInterestRate is \n" + annualInterestRate + "% , balance is " + balance;}
}
打印效果如下：
练习九：
统计 “a12 12bsk1928bc” 中的数字字符的数量；
方法一：运用字符在底层是数字存储，进行判断识别；
import java.util.Arrays;public class Demo {public static void main(String[] args) {String str = "a12 12bsk1928bc";int number = isNumber(str);System.out.println(number);}public static int isNumber(String str) {char[] charArray = str.toCharArray();int count = 0;for (int i = 0; i < charArray.length; i++) {if (charArray[i]>='0'&&charArray[i]<='9') {count++;}}return count;}
}
打印效果如下：
方法二：运用 Character 中 toString 方法将 str 转换成的字符数组转成 String 类型，然后正则表达式；
import java.util.Arrays;public class Demo {public static void main(String[] args) {String str = "a12 12bsk1928bc";int number = isNumber(str);System.out.println(number);}public static int isNumber(String str) {char[] charArray = str.toCharArray();int count = 0;for (int i = 0; i < charArray.length; i++) {String string = Character.toString(charArray[i]);if (string.matches("\\d")) {count++;}}return count;}
}
打印效果如下：
