java.lang.reflect.Field类的getBoolean()方法用于获取类中包含的静态或实例布尔字段的值。当一个类包含一个静态或实例布尔字段,而我们想获取该字段的值时,则可以使用此方法返回Field的值。
用法:
public boolean getBoolean(Object obj) throws IllegalArgumentException, IllegalAccessException
参数:此方法接受单个参数obj,该对象是要从中提取布尔值的对象。
返回值:此方法返回必需的布尔字段的值。
异常:此方法引发以下异常:
- IllegalAccessException:如果Field对象正在强制执行Java语言访问控制并且基础字段不可访问,则抛出此异常。
- IllegalArgumentException:如果指定的对象不是声明基础字段的类或接口的实例,或者如果不能通过扩展转换将字段值转换为布尔类型,则抛出此异常。
- NullPointerException :如果指定对象为null并且该字段是实例字段,则抛出此异常。
- ExceptionInInitializerError:如果此方法引发的初始化失败,则抛出此异常。
以下示例程序旨在说明getBoolean()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 isEmployee field object
Field field = User.class.getField("isEmployee");
// Apply getBoolean Method on User Object
// to get the value of isEmployee field
boolean value = field.getBoolean(user);
// print result
System.out.println("Value of Boolean Field"
+ " isEmployee is " + value);
// Now Get the isActive field object
field = User.class.getField("isActive");
// Apply getBoolean Method on User Object
// to get the value of isActive field
value = field.getBoolean(user);
// print result
System.out.println("Value of Boolean Field"
+ " isActive is " + value);
}
}
// sample User class
class User {
// static boolean values
public static boolean isEmployee = true;
public static boolean isActive = false;
public static boolean isEmployee()
{
return isEmployee;
}
public static void setEmployee(boolean isEmployee)
{
User.isEmployee = isEmployee;
}
public static boolean isActive()
{
return isActive;
}
public static void setActive(boolean isActive)
{
User.isActive = isActive;
}
}
输出:
Value of Boolean Field isEmployee is true
Value of Boolean Field isActive is false
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 mathDigit class object
mathDigit math = new mathDigit();
// Get the isEmployee field object
Field field = mathDigit.class.getField("isZero");
// Apply getBoolean Method on field Object
// to get the value of isZero field
boolean value = field.getBoolean(math);
// print result
System.out.println("Value: " + value);
}
// mathDigit class
static class mathDigit {
public static boolean isZero = false;
public int number;
public static boolean isZero()
{
return isZero;
}
public static void setZero(boolean isZero)
{
mathDigit.isZero = isZero;
}
public int getNumber()
{
return number;
}
public void setNumber(int number)
{
this.number = number;
}
}
}
输出:
Value: false
参考文献: https://docs.oracle.com/javase/10/docs/api/java/lang/reflect/Field.html#getBoolean(java.lang.Object)
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