java Method isSynthetic

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先看代码：

package com.reflect;import java.lang.reflect.Method;import junit.framework.TestCase;import static java.lang.System.out;public class TestSynthetic extends TestCase {public void testSynthetic() {try {Method[] methods = User.class.getDeclaredMethods();for (Method method : methods) {out.println(method.toString() + ", " + method.isSynthetic());}} catch (SecurityException e) {e.printStackTrace();}}class User {private int age;private String name;private User() {}private User(int age, String name) {this.age = age;this.name = name;}private int getAge() {return age;}private void setAge(int age) {this.age = age;}private String getName() {return name;}private void setName(String name) {this.name = name;}}}

运行testSynthetic，输出：

private java.lang.String com.reflect.TestSynthetic$User.getName(), falseprivate void com.reflect.TestSynthetic$User.setName(java.lang.String), falseprivate int com.reflect.TestSynthetic$User.getAge(), falseprivate void com.reflect.TestSynthetic$User.setAge(int), false

修改测试代码：

package com.reflect;import java.lang.reflect.Method;import junit.framework.TestCase;import static java.lang.System.out;public class TestSynthetic extends TestCase {public void testSynthetic() {try {User user = new User();user.age = 1;Method[] methods = User.class.getDeclaredMethods();for (Method method : methods) {out.println(method.toString() + ", " + method.isSynthetic());}} catch (SecurityException e) {e.printStackTrace();}}class User {private int age;private String name;private User() {}private User(int age, String name) {this.age = age;this.name = name;}private int getAge() {return age;}private void setAge(int age) {this.age = age;}private String getName() {return name;}private void setName(String name) {this.name = name;}}}

运行：

private java.lang.String com.reflect.TestSynthetic$User.getName(), falseprivate void com.reflect.TestSynthetic$User.setName(java.lang.String), falsestatic void com.reflect.TestSynthetic$User.access$1(com.reflect.TestSynthetic$User,int), trueprivate int com.reflect.TestSynthetic$User.getAge(), falseprivate void com.reflect.TestSynthetic$User.setAge(int), false

发现增加了一个方法：

static void com.reflect.TestSynthetic$User.access$1(com.reflect.TestSynthetic$User,int), true

这是编译器为这个类增加的，因为User这个内部类，全部的变量和方法，都是private的，但是外部程序要去调用，所以编译器做了这个工作。

上面只是修改了测试代码，并没有修改User这个内部类，就可以增加User的方法。

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