Java中的字段 getChar() 方法及示例

Java.lang.reflect.Field的getChar()方法用于获取 char 的值，该值必须是静态或实例字段类型。此方法还用于通过扩展转换获取可转换为 char 类型的另一个原始类型的值。当一个类包含一个静态或实例 Char 字段并且我们想要获取该字段的值时，我们可以使用此方法返回 Field 的值。

句法：

public char getChar(Object obj)
       throws IllegalArgumentException,
              IllegalAccessException

参数：此方法接受单个参数obj ，它是从中提取 char 值的对象。

返回值：该方法返回字段转换为char类型的值。

异常：此方法抛出以下异常：

1. IllegalAccessException：如果 Field 对象正在执行Java语言访问控制并且基础字段不可访问，则会引发此异常。
2. IllegalArgumentException：如果指定的对象不是声明基础字段的类或接口的实例，或者如果字段值无法通过扩展转换转换为 char 类型，则会引发此异常。
3. NullPointerException：如果指定对象为空且字段为实例字段，则抛出此异常。
4. ExceptionInInitializerError：如果此方法引发的初始化失败，则抛出此异常。

下面的程序说明了 getChar() 方法：
方案一：

// Java program to demonstrate the above method
  
import java.lang.reflect.Field;
  
public class GFG {
  
    public static void main(String[] args)
        throws NoSuchFieldException,
               SecurityException,
               IllegalArgumentException,
               IllegalAccessException
    {
  
        // Create the User class object
        User user = new User();
  
        // Get the identificationChar field object
        Field field
            = User.class.getField("identificationChar");
  
        // Apply getChar Method on User Object
        // to get the value of identificationChar field
        char value = field.getChar(user);
  
        // print result
        System.out.println("Value of Char Field"
                           + " identificationChar is "
                           + value);
  
        // Now Get the selectionChar field object
        field = User.class.getField("selectionChar");
  
        // Apply getChar Method on User Object
        // to get the value of selectionChar field
        value = field.getChar(user);
  
        // print result
        System.out.println("Value of Char Field"
                           + " selectionChar is "
                           + value);
    }
}
  
// sample User class
class User {
  
    // static char values
    public static char identificationChar = 'E';
    public static char selectionChar = 'A';
    public static String name = "Aman";
  
    // getter and setter methods
    public static char getIdentificationChar()
    {
        return identificationChar;
    }
  
    public static void
    setIdentificationChar(char identificationChar)
    {
        User.identificationChar = identificationChar;
    }
  
    public static char getSelectionChar()
    {
        return selectionChar;
    }
  
    public static void
    setSelectionChar(char selectionChar)
    {
        User.selectionChar = selectionChar;
    }
  
    public static String getName()
    {
        return name;
    }
  
    public static void setName(String name)
    {
        User.name = name;
    }
}

输出：

Value of Char Field identificationChar is E
Value of Char Field selectionChar is A

方案二：

// Java program to demonstrate the above method
  
import java.lang.reflect.Field;
  
public class GFG {
  
    public static void main(String[] args)
        throws NoSuchFieldException,
               SecurityException,
               IllegalArgumentException,
               IllegalAccessException
    {
  
        // Create the Alphabets class object
        Alphabets alphabet = new Alphabets();
  
        // Get the value field object
        Field field
            = Alphabets.class.getField("value");
  
        // Apply getChar Method on field Object
        // to get the value of value field
        char value = field.getChar(alphabet);
  
        // print result
        System.out.println("Value: " + value);
    }
  
    // Alphabets class
    static class Alphabets {
  
        // char field
        public static char value = 'Q';
  
        // getter and setter methods
        public static char getValue()
        {
            return value;
        }
  
        public static void setValue(char value)
        {
            Alphabets.value = value;
        }
    }
}

输出：

Value: Q

参考资料： https: Java/lang/reflect/Field.html#getChar-java.lang.Object-