在RandomAccessFile中结束行StringBuilder

我正在尝试使用类RandomAccessFile，但字符串有问题。

这是第一部分。写入文件：

public static void main(String[] args) throws IOException {
    File file = new File("/home/pep/java/randomFile.dat");
    RandomAccessFile fitxerAleatori = new RandomAccessFile(file, "rw");

    String[] surnames = { "SMITH", 
            "LOMU" };
    int[] dep = { 10,
            20 };
    Double[] salary = { 1200.50, 
            1200.50 };

    StringBuilder buffer = null;
    int n = surnames.length;

    for (int i = 0; i<n; i++){
        randomFile.writeInt(i+1); //ID
        buffer = new StringBuilder(surnames[i]);
        buffer.setLength(10); //10 characters
        randomFile.writeChars(buffer.toString());
        randomFile.writeInt(dep[i]);
        randomFile.writeDouble(salary[i]);
    }
    randomFile.close();
}

在第二部分中，我尝试读取此文件：

    File file = new File("/home/pep/java/randomFile.dat");
    RandomAccessFile randomFile = new RandomAccessFile(file, "r");

    char[] surname = new char[10];
    char aux;
    int id, dep, pos;
    Double salary;

    pos = 0;

    for (;;) {
        randomFile.seek(pos);
        id = randomFile.readInt();
        for (int i = 0; i < surname.length; i++) {
            aux = randomFile.readChar();
            surname[i] = aux;
        }
        String surnameStr = new String(surname); //HERE IS THE PROBLEM!!
        dep = randomFile.readInt();
        salary = randomFile.readDouble();
        System.out.println("ID: " + id + ", Surname: " + surnameStr + ", Departament: " + dep + ", Salary: " + salary);

        pos = pos + 36; // 4 + 20 + 4 + 8

        if (randomFile.getFilePointer() == randomFile.length())
            break;
    }
    randomFile.close();
}

好吧，当我希望读到：

ID：1，姓氏：SMITH，部门：10，工资：1200.50

我收到了：

ID：1，姓氏：SMITH

就像在姓氏中是行尾一样，因为如果我不显示姓氏，则其他信息是正确的。

谢谢！