Initial commit

Experiment/graph/Exp6/TransCard.mermaid

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+graph TD
+    subgraph pay 方法
+        P_A["开始 pay(amount)"] --> P_B{判断 amount > balance};
+        P_B -- true --> P_C[抛出 InsufficientBalanceException “余额不足”];
+        P_B -- false --> P_D[balance -= amount];
+        P_D --> P_E[打印 “支付成功，当前余额: ” + balance];
+        P_E --> P_F[结束 pay];
+        P_C --> P_F;
+    end
+
+    subgraph main 方法
+        M_A[开始 main] --> M_B[创建 TransCard 对象 card];
+        M_B --> M_C[设置 card.balance = 100.0];
+        M_C --> M_D{try 块};
+        M_D --> M_E["调用 card.pay(50.0)"];
+        M_E --> M_F["调用 card.pay(60.0)"];
+                M_F --> M_G[结束 try 块];
+        M_D -- InsufficientBalanceException --> M_H[捕获 InsufficientBalanceException];
+        M_H --> M_I["打印异常信息 e.getMessage()"];
+        M_I --> M_J[结束 main];
+        M_G --> M_J;
+    end