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;

}

运行结果：

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.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;

}

运行结果：

2