getDeclaredField()

getDeclaredField()和getField()方法都是获取字段的

getField 只能获取public的，包括从父类继承来的字段。

getDeclaredField 可以获取本类所有的字段，包括private的，但是不能获取继承来的字段。 (注： 这里只能获取到private的字段，但并不能访问该private字段的值,除非加上setAccessible(true))

因此在获取父类的私有属性时，要通过getSuperclass的之后再通过getDeclaredFiled获取

例子

// Java program to demonstrate the example 
// of Field getDeclaredField (String field_name) method of Class 
 
import java.lang.reflect.*;
 
public class GetDeclaredFieldOfClass {
    public static void main(String[] args) throws Exception {
        GetDeclaredFieldOfClass declare_field = new GetDeclaredFieldOfClass();
        // Get Class
        Class cl = declare_field.getClass();
 
        // By using getDeclaredField() method is to get the field of
        // the class 
        Field f = cl.getDeclaredField("i");
        System.out.println("Declared Field: " + f.toString());
    }
 
    // Private Constructors
    private GetDeclaredFieldOfClass() {
        System.out.println("We are in private constructor");
    }
 
    // Public Constructors
    public GetDeclaredFieldOfClass(int i) {
        this.i = i;
    }
    int i = 100;
}

输出

We are in private constructor
Declared Field: int GetDeclaredFieldOfClass.i