文件里面得是C#d代码，请给出相应得java代码

将给定的C#代码转换为Java代码需要考虑以下几个方面：

1. **数据类型的转换**：例如 `char` 在 Java 中是 Unicode 字符，而 C# 中可以是单字节字符。
2. **方法调用和类库的差异**：例如 `Thread.Sleep` 在 Java 中对应的是 `Thread.sleep`。
3. **异常处理**：Java 和 C# 的异常处理语法有所不同。
4. **字符串处理**：Java 使用 `StringBuilder` 或 `StringBuffer` 来处理字符串拼接。

以下是将给定的 C# 代码转换为 Java 代码的一个示例：

import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;

public class ICARD {
    public String sendICCard() {
        int comHandle = 0;
        int ret = 0;
        byte macAddr = 0;
        char[] recrodInfo = new char[1024];

        try {
            comHandle = K720CommOpenWithBaud("com2", 9600);
            if (comHandle < 1) {
                throw new Exception("打开端口com2失败");
            }

            for (int i = 0; i < 16; i++) {
                char[] recordInfo1 = new char[1000];
                int nRet = K720AutoTestMac(comHandle, (byte) i, recordInfo1);
                if (nRet == 0) {
                    macAddr = (byte) i;
                    break;
                }
            }

            ret = K720SendCmd(comHandle, macAddr, "RS", 2, recrodInfo);
            Thread.sleep(1000);

            byte[] stateInfo = new byte[3];
            ret = K720Query(comHandle, macAddr, stateInfo, recrodInfo);
            if (ret != 0) {
                throw new Exception("查询发卡器状态失败");
            }

            byte[] statesInfo = new byte[50];
            ret = K720SensorQuery(comHandle, macAddr, statesInfo, recrodInfo);
            if (ret == 0) {
                recodecardStatue(statesInfo);
            }

            if (statesInfo[3] == 0x32 || statesInfo[3] == 0x33 || statesInfo[3] == 0x36 ||
                statesInfo[3] == 0x38 || statesInfo[3] == 0x3B || statesInfo[3] == 0x3E ||
                statesInfo[3] == 0x31) {
                ret = K720SendCmd(comHandle, macAddr, "FC0", 3, recrodInfo);
                return "";
            }

            byte[] test = new byte[128];
            ret = K720SendCmd(comHandle, macAddr, "FC7", 3, recrodInfo);
            if (ret != 0) {
                throw new Exception("发卡到读卡位置失败");
            }

            Thread.sleep(300);
            ret = K720S70DetectCard(comHandle, macAddr, recrodInfo);

            // 扫描卡失败的部分被注释掉了
            // if (ret != 0) {
            //     throw new Exception("扫描卡失败");
            // }

            // 读取卡号的部分被注释掉了
            // byte[] cardNumber = new byte[128];
            // ret = D1000ReadCardNumber(comHandle, 0, cardNumber[0]);
            // ret = K720S70GetCardID(comHandle, macAddr, cardNumber, recrodInfo);

            // 设置密码
            String strPassword = "013014633987";
            byte[] password = stringToByteArray(strPassword);
            ret = K720S70LoadSecKey(comHandle, macAddr, 0x01, 0x30, password, recrodInfo);

            List<Byte> cardNumberList = new ArrayList<>();
            byte[] bData = new byte[16];
            ret = K720S70ReadBlock(comHandle, macAddr, (byte) 1, (byte) 2, bData, recrodInfo);
            for (byte b : bData) {
                cardNumberList.add(b);
            }

            if (ret != 0) {
                throw new Exception("获取卡号失败");
            }

            ret = K720SendCmd(comHandle, macAddr, "FC0", 3, recrodInfo);
            if (ret != 0) {
                throw new Exception("发卡失败");
            }

            StringBuilder result = new StringBuilder();
            for (byte b : bData) {
                result.append(String.format("%02X", b));
            }

            return result.toString();

        } catch (Exception ex) {
            ret = K720SendCmd(comHandle, macAddr, "CP", 2, recrodInfo);
            Util.webDBHelper.recordException(this.getClass().getName() + "sendICCard发卡器", ex.getMessage());
            return "";
        } finally {
            K720CommClose(comHandle);
        }
    }

    private static byte[] stringToByteArray(String s) {
        return s.getBytes(StandardCharsets.UTF_8);
    }

    // 假设这些方法在其他地方定义
    private static int K720CommOpenWithBaud(String port, int baudRate) {
        // 实现
        return 0;
    }

    private static int K720AutoTestMac(int comHandle, byte macAddr, char[] recordInfo) {
        // 实现
        return 0;
    }

    private static int K720SendCmd(int comHandle, byte macAddr, String cmd, int length, char[] recrodInfo) {
        // 实现
        return 0;
    }

    private static int K720Query(int comHandle, byte macAddr, byte[] stateInfo, char[] recrodInfo) {
        // 实现
        return 0;
    }

    private static int K720SensorQuery(int comHandle, byte macAddr, byte[] statesInfo, char[] recrodInfo) {
        // 实现
        return 0;
    }

    private static void recodecardStatue(byte[] statesInfo) {
        // 实现
    }

    private static int K720S70DetectCard(int comHandle, byte macAddr, char[] recrodInfo) {
        // 实现
        return 0;
    }

    private static int K720S70LoadSecKey(int comHandle, byte macAddr, byte sector, byte block, byte[] password, char[] recrodInfo) {
        // 实现
        return 0;
    }

    private static int K720S70ReadBlock(int comHandle, byte macAddr, byte sector, byte block, byte[] data, char[] recrodInfo) {
        // 实现
        return 0;
    }

    private static int K720CommClose(int comHandle) {
        // 实现
        return 0;
    }
}

### 主要变化点：
1. **数据类型**：将 `char` 数组转换为 `char` 数组或 `byte` 数组。
2. **异常处理**：使用 `try-catch-finally` 结构来处理异常，并在 `finally` 块中关闭通信端口。
3. **字符串处理**：使用 `StringBuilder` 来构建返回的字符串。
4. **线程睡眠**：使用 `Thread.sleep` 替换 `Thread.Sleep`。

请注意，上述代码中的某些方法（如 `K720CommOpenWithBaud`）需要根据实际的硬件接口进行实现。