feat(class41): 字符串功能理解，简单验证

- 新增 StringDemo1 类，演示字符串的创建和比较
- 实现简单的登录验证功能，包括用户名和手机号验证
- 展示字符串对象的创建方式和内容比较方法

src/class41/StringDemo1.java

@@ -0,0 +1,49 @@
+package class41;
+
+import java.util.Scanner;
+
+public class StringDemo1 {
+    public static void main(String[] args) {
+        String s1 = "hello"; //双引号直接创建的字符串对象，推荐
+        System.out.println(s1);
+        System.out.println(s1.length());
+
+
+        String s2 = new String("hello");
+        System.out.println(s2); //空字符串对象
+
+        System.out.println(s1 == s2); //比较两个字符串对象是否相等
+        System.out.println(s1.equals(s2));  //比较两个字符串对象的内容是否相等
+
+        String loginName = "admin";
+        System.out.println("请输入您的登陆名称");
+        Scanner sc = new Scanner(System.in);
+        String inputName = sc.next();
+        String number = "18888888888";
+        if(submit_login(loginName, inputName)){
+            if (check_number(number)){
+                System.out.println("登陆成功");
+            }
+            System.out.println("登陆失败，手机号验证错误");
+        }else{
+            System.out.println("登陆失败");
+        }
+
+
+
+
+    }
+    public static boolean submit_login(String loginName, String inputName){
+        return loginName.equals(inputName);
+    }
+    public static boolean check_number(String number){
+        Scanner sc = new Scanner(System.in);
+        System.out.println("请输入手机号验证：");
+        String phone = sc.next();
+        System.out.println("系统显示以下手机号进入：");
+        String newPhone = phone.substring(0,3) + "******" + phone.substring(9);
+        System.out.println(newPhone);
+        return number.equals(phone);
+    }
+}
+