Java Field setDouble()用法及代碼示例

java.lang.reflect.Field的setDouble()方法用於將字段的值設置為指定對象上的double。當需要將對象的字段值設置為double時，可以使用此方法在Object上設置值。

用法:

public void setDouble(Object obj, double d)
            throws IllegalArgumentException,
                   IllegalAccessException

參數：此方法接受接受兩個參數：

obj：是應該修改其字段的對象，並且
d：這是要修改的obj字段的新值。

返回：此方法不返回任何內容。

異常：此方法引發以下異常：

IllegalAccessException：如果此Field對象正在強製執行Java語言訪問控製，並且基礎字段是不可訪問的或最終的。
IllegalArgumentException：如果指定的對象不是聲明基礎字段(或其子類或實現者)的類或接口的實例，或者展開轉換失敗。
NullPointerException：如果指定的對象為null，並且該字段是實例字段。
ExceptionInInitializerError：如果此方法引發的初始化失敗。

以下示例程序旨在說明setDouble()方法：
示例1:

// Java program to illustrate setDouble() method 
  
import java.lang.reflect.Field; 
  
public class GFG { 
  
    public static void main(String[] args) 
        throws Exception 
    { 
  
        // create user object 
        Employee emp = new Employee(); 
  
        // print value of salary 
        System.out.println( 
            "Value of salary before "
            + "applying setDouble is "
            + emp.salary); 
  
        // Get the field object 
        Field field = Employee.class
                          .getField("salary"); 
  
        // Apply setDouble Method 
        field.setDouble(emp, 50000.99); 
  
        // print value of salary 
        System.out.println( 
            "Value of salary after "
            + "applying setDouble is "
            + emp.salary); 
  
        // print value of pf 
        System.out.println( 
            "Value of pf before "
            + "applying setDouble is "
            + emp.pf); 
  
        // Get the field object 
        field = Employee.class.getField("pf"); 
  
        // Apply setDouble Method 
        field.setDouble(emp, 1234.34); 
  
        // print value of pf 
        System.out.println( 
            "Value of pf after "
            + "applying setDouble is "
            + emp.pf); 
    } 
} 
  
// sample class 
class Employee { 
  
    // static double values 
    public static double pf = 2342.89; 
    public static double salary = 43125; 
}

輸出：

Value of salary before applying setDouble is 43125.0
Value of salary after applying setDouble is 50000.99
Value of pf before applying setDouble is 2342.89
Value of pf after applying setDouble is 1234.34

示例2:

// Java program to illustrate setDouble() method 
  
import java.lang.reflect.Field; 
  
public class GFG { 
  
    public static void main(String[] args) 
        throws Exception 
    { 
  
        // create Numbers object 
        Numbers no = new Numbers(); 
  
        // Get the value field object 
        Field field = Numbers.class
                          .getField("value"); 
  
        // Apply setDouble Method 
        field.setDouble(no, 53245.466); 
  
        // print value of isActive 
        System.out.println( 
            "Value after "
            + "applying setDouble is "
            + Numbers.value); 
    } 
} 
  
// sample Numbers class 
class Numbers { 
  
    // static double value 
    public static double value = 1232.3685; 
}

輸出：

Value after applying setDouble is 53245.466

參考： https://docs.oracle.com/javase/8/docs/api/java/lang/reflect/Field.html#setDouble-java.lang.Object-double-

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注：本文由純淨天空篩選整理自AmanSingh2210大神的英文原創作品 Field setDouble() method in Java with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。