Java Field getChar()用法及代碼示例

java.lang.reflect.Field的getChar()方法用於獲取必須為靜態或實例字段類型的char值。此方法還用於通過擴展轉換獲取可轉換為char類型的另一個基本類型的值。當一個類包含一個靜態或實例Char字段並且我們想要獲取該字段的值時，我們可以使用此方法返回Field的值。

用法:

public char getChar(Object obj)
       throws IllegalArgumentException,
              IllegalAccessException

參數：此方法接受單個參數obj，這是從中提取char值的對象。

返回值：此方法返回轉換為char類型的字段的值。

異常：此方法引發以下異常：

IllegalAccessException：如果Field對象正在強製執行Java語言訪問控製並且基礎字段不可訪問，則拋出此異常。
IllegalArgumentException：如果指定的對象不是聲明基礎字段的類或接口的實例，或者無法通過擴展轉換將字段值轉換為char類型，則拋出此異常。
NullPointerException ：如果指定對象為null並且該字段是實例字段，則拋出此異常。
ExceptionInInitializerError：如果此方法引發的初始化失敗，則拋出此異常。

以下示例程序旨在說明getChar()方法：
示例1:

// 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; 
    } 
}

輸出：

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

示例2:

// 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; 
        } 
    } 
}

輸出：

Value: Q

參考文獻： https://docs.oracle.com/javase/8/docs/api/java/lang/reflect/Field.html#getChar-java.lang.Object-

相關用法

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