Java中的类 getDeclaredFields() 方法和示例

Java.lang.Class 类的getDeclaredFields()方法用于获取该类的字段，这些字段是private、public、protected 或default 及其成员，但不包括继承的字段。该方法以 Field 对象数组的形式返回该类的字段。
句法：

public Field[] getDeclaredFields()
               throws SecurityException

参数：此方法不接受任何参数。
返回值：该方法以Field对象数组的形式返回该类的字段。
异常如果存在安全管理器并且不满足安全条件，则此方法将引发SecurityException 。
下面的程序演示了 getDeclaredFields() 方法。
示例 1：

Java

// Java program to demonstrate getDeclaredFields() method
 
import java.util.*;
 
public class Test {
    public static void main(String[] args)
        throws ClassNotFoundException
    {
 
        // returns the Class object for this class
        Class myClass = Class.forName("Test");
 
        System.out.println("Class represented by myClass: "
                           + myClass.toString());
 
        // Get the fields of myClass
        // using getDeclaredFields() method
        System.out.println(
            "DeclaredFields of myClass: "
            + Arrays.toString(
                  myClass.getDeclaredFields()));
    }
}

输出：

Class represented by myClass: class Test
DeclaredFields of myClass: []

示例 2：

Java

// Java program to demonstrate getDeclaredFields() method
 
import java.util.*;
 
class Main {
 
    public Object obj;
 
    Main()
    {
 
        class Arr {
        };
 
        obj = new Arr();
    }
 
    public static void main(String[] args)
        throws ClassNotFoundException
    {
        // returns the Class object for this class
        Class myClass = Class.forName("Main");
 
        System.out.println("Class represented by myClass: "
                           + myClass.toString());
 
        // Get the fields of myClass
        // using getDeclaredFields() method
        System.out.println(
            "DeclaredFields of myClass: "
            + Arrays.toString(
                  myClass.getDeclaredFields()));
    }
}

输出：

Class represented by myClass: class Main
DeclaredFields of myClass: [public java.lang.Object Main.obj]

参考： https://docs.oracle.com/javase/9/docs/api/ Java/lang/Class.html#getDeclaredFields–