finally 確保清理與重試模式構建健壯代碼

finally 必執行示範

while (true) {
    try {
        if (count++ == 0) throw new Exception();
        System.out.println("No exception");
    } catch (Exception e) {
        System.out.println("Exception thrown");
    } finally {
        System.out.println("in finally clause");
        if (count == 2) break;
    }
}

輸出證明 finally 無論有無異常都執行。

重試模式

將 try 置於迴圈，配合計數器限制重試次數，實現「嘗試→失敗→清理→重試」健壯流程。

int attempts = 0;
while (attempts < MAX) {
    try {
        riskyOperation();
        break;
    } catch (TransientException e) {
        attempts++;
    } finally {
        cleanup();
    }
}

意義

彌補 Java 異常無法「恢復至拋出點」的限制，透過迴圈重試實現語義上的恢復。