使用反射修改final属性

情型1：static final属性，无法修改其值。

package m5.d7;  
  
import java.lang.reflect.Field;  
  
public class FieldTest {  
    public static void main(String[] args) {  
        try {  
            A a = new A();  
  
            Field field = a.getClass().getDeclaredField("a");  
  
            field.setAccessible(true);  
  
            field.set(a, 2);  
  
            System.out.println(field.get(a));  
        } catch (SecurityException e) {  
            e.printStackTrace();  
        } catch (NoSuchFieldException e) {  
            e.printStackTrace();  
        } catch (IllegalArgumentException e) {  
            e.printStackTrace();  
        } catch (IllegalAccessException e) {  
            e.printStackTrace();  
        }  
    }  
}  
  
class A {  
    private static final int a = 1;  
}  

运行

java.lang.IllegalAccessException: Can not set static final int field m5.d7.A.a to java.lang.Integer  
    at sun.reflect.UnsafeFieldAccessorImpl.throwFinalFieldIllegalAccessException(Unknown Source)  
    at sun.reflect.UnsafeFieldAccessorImpl.throwFinalFieldIllegalAccessException(Unknown Source)  
    at sun.reflect.UnsafeQualifiedStaticIntegerFieldAccessorImpl.set(Unknown Source)  
    at java.lang.reflect.Field.set(Unknown Source)  
    at m5.d7.FieldTest.main(FieldTest.java:16)  

情型2：final属性，可以修改其值。

package m5.d7;  
  
import java.lang.reflect.Field;  
  
public class FieldTest {  
    public static void main(String[] args) {  
        try {  
            A a = new A();  
  
            Field field = a.getClass().getDeclaredField("a");  
  
            field.setAccessible(true);  
  
            field.set(a, 2);  
  
            System.out.println(field.get(a));  
        } catch (SecurityException e) {  
            e.printStackTrace();  
        } catch (NoSuchFieldException e) {  
            e.printStackTrace();  
        } catch (IllegalArgumentException e) {  
            e.printStackTrace();  
        } catch (IllegalAccessException e) {  
            e.printStackTrace();  
        }  
    }  
}  
  
class A {  
    private final int a = 1;  
}  

运行

2