Java反射机制，是在程序的运行过程中，对于任何一个类，都可能晓得它的所有属性和办法。对于任意一个对象，都可能晓得调用他的任意属性和办法。这种动静获取信息以及动静调用对象办法的性能称为Java语言的反射机制。
如下代码示例：
- 父类Animal
package com.study.reflection;public class Animal { public String name; public int age; public Animal() { super(); } public Animal(String name, int age) { this.name = name; this.age = age; } public void eat() { } public String getInfo() { return "name:" + this.name + ", age:" + age; }}- 子类Cat，继承Animal
package com.study.reflection;public class Cat extends Animal { public String color; private String owner; String sex; public Cat() { super(); } public Cat(String name, int age, String color, String owner) { super(name, age); this.color = color; this.owner = owner; } public Cat(String owner) { this.owner = owner; } public String getColor() { return color; } public void setColor(String color) { this.color = color; } void mie() { } private void smile() { System.out.println(name + "在笑"); } public void cry() { System.out.println(name + "在哭"); } @Override public String toString() { return "姓名：" + this.name + ", 年龄：" + this.age + ", 色彩：" + color + ", 客人：" + owner; }}- 测试类TestReflect
package com.study.reflection;import java.lang.reflect.Constructor;import java.lang.reflect.Field;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;public class TestReflect { public static void main(String[] args) { Class cat = null; try { cat = Class.forName("com.study.reflection.Cat"); } catch (ClassNotFoundException e) { e.printStackTrace(); } //获取对象的所有私有（public）属性，例如：public String color;包含继承的父类中public润饰的属性 Field[] fields = cat.getFields(); for (Field f : fields) { //输入后果： // public java.lang.String com.study.reflection.Cat.color // public java.lang.String com.study.reflection.Animal.name // public int com.study.reflection.Animal.age System.out.println(f); } System.out.println("=========================================================="); //获取对象所有属性（不论是public还是private或者没有修饰符的润饰的属性），但不包含继承的父类中的属性 Field[] declaredFields = cat.getDeclaredFields(); for (Field df : declaredFields) { //输入后果： //public java.lang.String com.study.reflection.Cat.color //private java.lang.String com.study.reflection.Cat.owner //java.lang.String com.study.reflection.Cat.sex System.out.println(df); } System.out.println("=========================================================="); //获取对象的所有公共（public）办法;包含继承的父类中的public润饰的办法以及Object类中public润饰的办法 Method[] methods = cat.getMethods(); for (Method m : methods) { //输入后果： //public java.lang.String com.study.reflection.Cat.toString() //public void com.study.reflection.Cat.setColor(java.lang.String) //public java.lang.String com.study.reflection.Cat.getColor() //public void com.study.reflection.Cat.cry() //public void com.study.reflection.Animal.eat() //public java.lang.String com.study.reflection.Animal.getInfo() //public final void java.lang.Object.wait(long,int) throws java.lang.InterruptedException //public final void java.lang.Object.wait() throws java.lang.InterruptedException //public final native void java.lang.Object.wait(long) throws java.lang.InterruptedException //public boolean java.lang.Object.equals(java.lang.Object) //public native int java.lang.Object.hashCode() //public final native java.lang.Class java.lang.Object.getClass() //public final native void java.lang.Object.notify() //public final native void java.lang.Object.notifyAll() System.out.println(m); } System.out.println("=========================================================="); //获取对象所有办法（不论是public还是private或者没有修饰符的润饰的办法），但不包含继承的父类中的办法 Method[] declaredMethods = cat.getDeclaredMethods(); for (Method dm : declaredMethods) { //输入后果： //public java.lang.String com.study.reflection.Cat.toString() //public void com.study.reflection.Cat.setColor(java.lang.String) //public java.lang.String com.study.reflection.Cat.getColor() //void com.study.reflection.Cat.mie() //private void com.study.reflection.Cat.smile() //public void com.study.reflection.Cat.cry() System.out.println(dm); } System.out.println("=========================================================="); //获取对象的所有公共（public）构造方法，但不包含继承的父类中的构造方法 Constructor[] constructors = cat.getConstructors(); for (Constructor c : constructors) { //输入后果： //public com.study.reflection.Cat(java.lang.String) //public com.study.reflection.Cat(java.lang.String,int,java.lang.String,java.lang.String) //public com.study.reflection.Cat() System.out.println(c); } System.out.println("=========================================================="); //获取对象的所有构造方法， Constructor[] declaredConstructors = cat.getDeclaredConstructors(); for (Constructor dc : declaredConstructors) { //输入后果： //public com.study.reflection.Cat(java.lang.String) //public com.study.reflection.Cat(java.lang.String,int,java.lang.String,java.lang.String) //public com.study.reflection.Cat() System.out.println(dc); } System.out.println("=========================================================="); //Cat cat1 = (Cat) cat.newInstance();//此办法在Java9之后显示已过期 Constructor<Cat> constructor = null; try { //获取全参数构造函数 constructor = cat.getConstructor(String.class, int.class, String.class, String.class); } catch (NoSuchMethodException e) { e.printStackTrace(); } Cat cat1 = null; try { //应用构造函数赋值初始化 cat1 = constructor.newInstance("花花", 2, "红色", "小明"); } catch (InstantiationException e) { e.printStackTrace(); } catch (IllegalAccessException e) { e.printStackTrace(); } catch (InvocationTargetException e) { e.printStackTrace(); } //输入后果： //姓名：花花, 年龄：2, 色彩：红色, 客人：小明 System.out.println(cat1); System.out.println("=========================================================="); //获取指定办法，并执行，【获取的办法必须是public润饰的】 Method cry = null; try { //输入后果： //花花在哭 cry = cat.getMethod("cry");//cry()办法 } catch (NoSuchMethodException e) { e.printStackTrace(); } Object object = null; try { object = cry.invoke(cat1);//调用cry()办法 } catch (IllegalAccessException e) { e.printStackTrace(); } catch (InvocationTargetException e) { e.printStackTrace(); } }}