Java Field setDouble()用法及代码示例

java.lang.reflect.Field的setDouble()方法用于将字段的值设置为指定对象上的double。当需要将对象的字段值设置为double时，可以使用此方法在Object上设置值。

用法:

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

参数：此方法接受接受两个参数：

obj：是应该修改其字段的对象，并且
d：这是要修改的obj字段的新值。

返回：此方法不返回任何内容。

异常：此方法引发以下异常：

IllegalAccessException：如果此Field对象正在强制执行Java语言访问控制，并且基础字段是不可访问的或最终的。
IllegalArgumentException：如果指定的对象不是声明基础字段(或其子类或实现者)的类或接口的实例，或者展开转换失败。
NullPointerException：如果指定的对象为null，并且该字段是实例字段。
ExceptionInInitializerError：如果此方法引发的初始化失败。

以下示例程序旨在说明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; 
}

输出：

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; 
}

输出：

Value after applying setDouble is 53245.466

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

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注：本文由纯净天空筛选整理自AmanSingh2210大神的英文原创作品 Field setDouble() method in Java with Examples。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。