java如何检查列表中的数据是否包含0或空值并删除该数据

Question

下面是我迄今为止创建的代码。 也就是说，下面的程序正在读取该文件，如果给定文件中的一个字段为空，那么它将为整数值打印0，为字符串值打印null

// Override all the methods of the DataManager Interface
public class StudentDataManager implements DataManager {
    List<Student> list = new ArrayList<Student>();

    @SuppressWarnings("null")
    @Override
    public List<Student> populateData(String fileName) {

        Scanner s = null;
        String nameAndRollNumber = "";
        String numbers[] = null;
        Integer roll1 = 0;
        String roll = null;
        String name = null;
        String age = null;
        String zip = null;
        String street = null;
        String city = null;
        Integer age1 = 0;
        String cpmletedata = null;
        try {
            s = new Scanner(new File("F:\\...\\StudentDetails.txt"));

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }

        while (s.hasNext()) {
            nameAndRollNumber = s.nextLine();
            String[] nameAndRollNumbers = nameAndRollNumber.split(",");
            try {
                roll = nameAndRollNumbers[0];
                roll1 = Integer.valueOf(roll);
                cpmletedata = " " + roll;
                name = nameAndRollNumbers[1];

                if (nameAndRollNumbers[1].equals("")) {
                    cpmletedata = cpmletedata + " null ";
                } else {
                    cpmletedata = cpmletedata + " " + name;
                }

                age = nameAndRollNumbers[2];

                if (nameAndRollNumbers[2].equals("")) {
                    cpmletedata = cpmletedata + " 0 ";
                } else {
                    age1 = Integer.valueOf(age);
                    cpmletedata = cpmletedata + " " + age1;
                }

                street = nameAndRollNumbers[3];
                if (nameAndRollNumbers[3].equals("")) {
                    cpmletedata = cpmletedata + " null ";
                } else {
                    cpmletedata = cpmletedata + " " + street;
                }

                city = nameAndRollNumbers[4];
                if (nameAndRollNumbers[4].equals("")) {
                    // System.out.print("null");
                    cpmletedata = cpmletedata + " null ";
                } else {
                    // System.out.print(city + " ");
                    cpmletedata = cpmletedata + " " + city;
                }

                zip = nameAndRollNumbers[5];

                if (nameAndRollNumbers[5].equals(" ")) {
                    cpmletedata = cpmletedata + " null ";
                } else {
                    cpmletedata = cpmletedata + " " + zip;
                }

                Address a1 = new Address(street, city, zip);
                cpmletedata = cpmletedata + " ";
                System.out.println(cpmletedata);
                list.add(new Student(roll1, name, age1, a1));
            }

            catch (Exception e) {
                e.printStackTrace();
            }
        }

        s.close();
        return list;
    }
}

现在我有这么多的代码，它给出了以下输出：

 1 Arjun 12 GhandiNagar Pune 411020 
 2 Deep 8 M.G.Road Mumbai 411032 
 3 Deep 3 F.C.Road Pune 411032 
 4 Neha 10 Camp Pune 411023 
 5 Seema 0  null  null  null  
 6 Bani 6 Camp Mumbai 411045 
 7 Deepali 3 M.G.Road Mumbai 411032 
 8 Neha 0  null  Mumbai null  
 9 Meena 9 Nariman Point Mumbai 411045 
 10 Chaitali 3 M.G.Road Mumbai 411032 
 11 Bani 6 Camp Mumbai 411045 
 12 Deepali 3 M.G.Road Mumbai 411032 
 13 Neha 10 F.C. Road Pune 411023 
 14 Deep 3 F.C.Road Pune 411032 
 15 Beena 6 Camp Mumbai 411045 

另一个功能是验证数据。也就是说，如果记录包含0或null，我们必须使其无效，也就是说，我们必须删除该特定行并将异常作为InsufficientDataException抛出。我创造了这个例外，但我不明白。如何再次读取该列表并检查行是否包含0或null并验证它

Answer 1

如果修改当前学生列表，它将抛出一个异常， 因此，创建另一个学生列表，条件是只选择所需的 参赛将是一个很好的方法，如下所示：

---

public void validateData(List<Student> studentList)
        throws InsufficientDataException {
    List<Student> studentList2 = new ArrayList<Student>();
    // studentList2.addAll(studentList);

    int i = 0;
    for (Student s : studentList) {

        i++;
        if ((s.getRollno() == 0) || (s.getStudentName() == "null")
                || (s.getAge() == 0)
                || (s.getAddress().getStreetName() == "null")
                || (s.getAddress().getCity() == "null")
                || (s.getAddress().getZipCode() == "null")) {
        } else {
            studentList2.add(s);
        }
    }

    for (Student s : studentList2) {
        System.out.println(s.getRollno() + "  " + s.getStudentName() + "  "
                + s.getAge() + "  " + s.getAddress().getStreetName() + "  "
                + s.getAddress().getCity() + "  "
                + s.getAddress().getZipCode());
    }

}

下面是您想要的输出（过滤）：

---

1  Arjun  12  GhandiNagar  Pune  411020
2  Deep  8  M.G.Road  Mumbai  411032
3  Deep  3  F.C.Road  Pune  411032
4  Neha  10  Camp  Pune  411023
6  Bani  6  Camp  Mumbai  411045
7  Deepali  3  M.G.Road  Mumbai  411032
9  Meena  9  Nariman Point  Mumbai  411045
10  Chaitali  3  M.G.Road  Mumbai  411032
11  Bani  6  Camp  Mumbai  411045
12  Deepali  3  M.G.Road  Mumbai  411032
13  Neha  10  F.C. Road  Pune  411023
14  Deep  3  F.C.Road  Pune  411032
15  Beena  6  Camp  Mumbai  411045

Answer 2

您可以创建一个validate（）：boolean方法，该方法读取数组的每个条目，并测试是否存在0或null值。如果检测到这种情况，则返回false，否则在方法末尾返回true

Answer 3

我这边的一个可能的解决方案和建议是使用来自org.apache.commons的CollectionUtils：

List<Student> lAllStudent = lStudentDataManager.populateData("testfile.txt");
int lOldSize = lAllStudent.size();
CollectionUtils.filter(lAllStudent, new ListSelector<Student>() {

  @Override
  public boolean select(int pIndex, Student pInput) {
    if (pInput.getAge()==0 || pInput.getZip() == null || pInput.getStreet() == null || pInput.getCity() == null){
      return false;  
    }
    return true;
  }
});
if (lOldSize != lAllStudent.size()){
  throw new InsufficientDataException();
}

如果select返回false，元素将从列表中删除。 调用filter后，可以将列表的旧大小与新大小进行比较。如果当前大小和旧大小之间存在差异，则某些元素已被删除，您可以抛出exception