使用反射修改final属性

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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.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