如何正确测试自定义对象中的 char[ ] 字段是否存在空值、空白或空值？为什么 char[ ] 表示长度为 11？

Question

我正在研究如何使用反射来初始化自定义对象。举个例子，我的对象有几个不同类型的字段，但是 NONE 个字段属于字符串类型。我使用 chararrays 而不是字符串，因为我想清除对象如果应用程序崩溃，不用担心堆中存在不可变字符串。

此外，由于 class 实现了 CharSequence，静态字段 buff、offset 和 count 是必需的。另外值得一提的是，getters 和 setters 是 synchronized 因为这个对象将在多线程环境中使用。最后，有一个名为 People 的自定义 Person 对象列表，它位于自己的 People.java 文件中，并且是 Person 对象的自定义集合。为简洁起见，省略了有关该对象的其他详细信息。

问题是，如何测试我的 Person 对象中的空字段、空白字段或 null 字段？在我的主要 class，在将所述对象插入后端数据库之前，我想测试 null、empty 或 blank。我有尝试创建一个 Person.isNull() 和一个类似的 Person.hasNull() 函数来测试空值在 char[] 字段中，但结果绝对不是我的预期。里面的println语句 isCharArray 的测试揭示了一些我目前不理解的东西......

这是一些示例输出：

Size of byte: 1 bytes.
Size of short: 2 bytes.
Size of int: 4 bytes.
Size of long: 8 bytes.
Size of char: 2 bytes.
Size of float: 4 bytes.
Size of double: 8 bytes.
buff: char[] 11
personID: char[] 11
personTitle: char[] 11
personFirstName: char[] 11
personLastName: char[] 11

它是使用以下 System.out.println 语句创建的：

System.out.println(f.getName() + ": " + f.getType().getCanonicalName() + " " +  String.valueOf(value).length());

并提出了 2 个问题：

为什么是 11？！！！！！！
如何正确测试空白、空白或零长度字段？！！！

请帮忙....

public class Person  implements Serializable, 
                                Comparable<Person>,  
                                CharSequence, 
                                Cloneable   { // the object to model

    //  Fields 0, 1, and 2 are required to implement CharSequence                                   
    //  http://www.java2s.com/Tutorial/Java/0040__Data-Type/implementsCharSequence.htm
    private  static char[] buff = {'[=12=]'};   // No static fields are ever                    // Field 0
    private  static int offset  = 0;        // written to file. Their values                // Field 1
    private  static int count   = 0;        // must be reconstructed.                       // Field 2  

    // default serialVersion id
    private static final long serialVersionUID = 7891011129876814235L;                      // Field 3
    private final static LocalDateTime rightNow = LocalDateTime.now();  

    private long   localSerialVersionUID= serialVersionUID;  //1st field written to file    // Field 4  
    private LocalDateTime personCreatedDateTime= rightNow;                                  // Field 5 
    private LocalDateTime  personLastUpdate    =  rightNow; // (YYYY-MM-DD)                 // Field 6  
    private char[] personID              = {'[=12=]'}; // (PK)  possibly int auto increment     // Field 7 
    private char[] personTitle           = {'[=12=]'};                                          // Field 8 
    private char[] personFirstName       = {'[=12=]'};                                          // Field 9 
    private char[] personLastName        = {'[=12=]'};                                          // Field 10 
    private LocalDate   personDOB        =  LocalDate.parse("1010-10-10"); // (YYYY-MM-DD)  // Field 11



    public Person( 
            final long serialUID,                           //4        
            final LocalDateTime createdDateTime,            //5 
            final LocalDateTime lastUpdate,                 //6
            final char[] id,                                //7 
            final char[] title,                             //8 
            final char[] firstName,                         //9 
            final char[] lastName,                          //10 
            final LocalDate   DOB                           //11                                                   
    ) {                                                
        this.localSerialVersionUID(serialUID);           //4 
        this.personCreatedDateTime(LocalDateTime.now()); //5 
        this.personLastUpdate(lastUpdate);               //6
        this.personID(id);                               //7 
        this.personTitle(title);                         //8 
        this.personFirstName(firstName);                 //9 
        this.personLastName(lastName);                   //10
        this.personDOB(DOB);                             //11
    }   

    public boolean hasNull() {
        Field fields[] = this.getClass().getDeclaredFields();

        for (Field f : fields) {
            f.setAccessible(true);

            try{
                    Object value = f.get(this);
                    if ( value == null) {return true; } // default condition

                    boolean isCharArray =  f.getType().getCanonicalName().equals("char[]" );


                    // No need to check fields that are not char[]
                    if (( isCharArray) ) {      

    // ************* this compiles and executes (doesn't crash), but it doesn't produce intended results *********

                        System.out.println(f.getName() + ": " + f.getType().getCanonicalName() + " " +  String.valueOf(value).length());

                        if ( String.valueOf(value).length() == 0)  {return true;}
                        if ( String.valueOf(value).isEmpty())      {return true;}
                        if ( String.valueOf(value).isBlank())      {return true;}
                        if ( String.valueOf(value).equals('[=12=]'))   {return true;}

                    }   

    // ************* this compiles and executes (doesn't crash), but it doesn't produce intended results *********


                } catch (IllegalArgumentException e) {
                // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (IllegalAccessException e) {
                // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
            return false;
        }
    }         


    //enter code here


    /**
     * @param args
     */
    public static void main(String[] args)  {
        People<Person> people = new People()<>; //customized list of person objects
        People<Person> people2 = new People()<>; //customized list of person objects

        Person thomas = new Person().personFirstName("Thomas".toCharArray()); 
                // all other char array fields = {'[=12=]'}
        people.add(thomas);

        Person sybil =  new Person().personFirstName("Sybil".toCharArray()); 
                // all other char array fields = {'[=12=]'}
        people2.add(sybil);

        if (!thomas.hasNull() ){    // ******* currently this test fails and a Person gets inserted to the People list
            People.insertPerson(thomas);
        }
        if (!sybil.hasNull() ){     // ******* currently this test fails and a Person gets inserted to the People list
            People.insertPerson(sybil);
        }
    }
}

Answer 1

String.valueOf().length() returns 11 因为这是输出中 digits/characters 的数量（即 [@936016386 - 一个地址 - 有 11 个字符）

如何正确测试自定义对象中的 char[ ] 字段是否存在空值、空白或空值？为什么 char[ ] 表示长度为 11？

How do I properly test the char[ ] fields in my custom object for nulls, blanks, or empty? and Why do char[ ] indicate a length of 11?

java

arrays

reflection

serialization

initialization