实例讲解Java基础之反射

实例讲解Java基础之反射

前期准备

编写一个真实类phone,实现list接口

public class Phone implements List {

public double price;

public String name;

public Phone() {

}

public Phone(double price, String name) {

this.price = price;

this.name = name;

}

public double getPrice() {

return price;

}

public void gege(String h){

System.out.println("gege的"+h);

}

public void setPrice(double price) {

this.price = price;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

@Override

public String toString() {

return "Phone{" +

"price=" + price +

", name='" + name + '\'' +

'}';

}

@Override

public int size() {

return 0;

}

@Override

public boolean isEmpty() {

return false;

}

@Override

public boolean contains(Object o) {

return false;

}

@Override

public Iterator iterator() {

return null;

}

@Override

public Object[] toArray() {

return new Object[0];

}

@Override

public boolean add(Object o) {

return false;

}

@Override

public boolean remove(Object o) {

return false;

}

@Override

public boolean addAll(Collection c) {

return false;

}

@Override

public boolean addAll(int index, Collection c) {

return false;

}

@Override

public void clear() {

}

@Override

public Object get(int index) {

return null;

}

@Override

public Object set(int index, Object element) {

return null;

}

@Override

public void add(int index, Object element) {

}

@Override

public Object remove(int index) {

return null;

}

@Override

public int indexOf(Object o) {

return 0;

}

@Override

public int lastIndexOf(Object o) {

return 0;

}

@Override

public ListIterator listIterator() {

return null;

}

@Override

public ListIterator listIterator(int index) {

return null;

}

@Override

public List subList(int fromIndex, int toIndex) {

return null;

}

@Override

public boolean retainAll(Collection c) {

return false;

}

@Override

public boolean removeAll(Collection c) {

return falshttp://e;

}

@Override

public boolean containsAll(Collection c) {

return false;

}

@Override

public Object[] toArray(Object[] a) {

return new Object[0];

}

}

1.反射之4种new对象

public class Test2 {

public static void main(String[] args) throws IllegalAccessException, InstantiationException, ClassNotFoundException {

//第一种

Phone p = new Phone(2999,"小米");

System.out.println(p);//Phone{price=2999.0, name='小米'}

//第二种 需要一个空参构造

Class phoneClass = Phone.class;

Phone phone = phoneClass.newInstance();

phone.setName("华为");

phone.setPrice(3499);

System.out.println(phone);//Phone{price=3499.0, name='华为'}

//第三种

Class> aclass = Class.forName("com.demo.bean.Phone");

Phone p2 = (Phone) aclass.newInstance();

p2.setPrice(2999);

p2.setName("魅族");

System.out.println(p2);//Phone{price=2999.0, name='魅族'}

//第四种,需要一个配置文件phone.properties

String name = ResourceBundle.getBundle("phone").getString("myphone");

Class> bClass = Class.forName(name);

Phone p3 = (Phone) bClass.newInstance();

p3.setPrice(3299);

p3.setName("锤子");

System.out.println(p3);//Phone{price=3299.0, name='锤子'}

}

}

配置文件phone.properties

myphone=com.demo.bean.Phone

2. 反射之获取类、父类、实现接口

public class Test3 {

public static void main(String[] args) throws ClassNotFoundException {

String string = ResourceBundle.getBundle("phone").getString("myphone");

Class> aClass = Class.forName(string);

//获取类的完整路径

System.out.println(aClass.getName());//com.demo.bean.Phone

//获取类的简单名字

System.out.println(aClass.getSimpleName());//Phone

//获取类的父类

Class> superclass = aClass.getSuperclass();

System.out.println(superclass.getName());//java.lang.Object

System.out.println(superclass.getSimpleName());//Object

//获得类的接口

Class>[] interfaces = aClass.getInterfaces();

for (Class> in:interfaces

) {

System.out.println(in.getSimpleName());

}

}

}

3.反射之获取空参、有参构造

public class Test4 {

public static void main(String[] args) throws ClassNotFoundException, IllegalAccessException, InstantiationException, NoSuchMethodException {

String string = ResourceBundle.getBundle("phone").getString("myphone");

Class> aClass = Class.forName(string);

//调用的是无参的构造方法

Phone p1 = (Phone) aClass.newInstance();

p1.setName("华为");

p1.setPrice(2999);//Phone{price=2999.0, name='华为'}

System.out.println(p1);

//获得无参的构造方法

Constructor> constructor = aClass.getConstructor();

System.out.println(constructor);//public com.demo.bean.Phone()

//获得所有的构造方法

Constructor>[] constructors = aClass.getConstructors();

for (Constructor> c:constructors

) {

System.out.println(c);

}

}

}

4.反射之获取方法

public class Test5 {

public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException,InstantiationException,IllegalAccessException,InvocationTargetException{

String string = ResourceBundle.getBundle("phone").getString("mhttp://yphone");

Class> aClass = Class.forName(string);

//包含了父类的方法

Method[] methods = aClass.getMethods();

for (Method m:methods

) {

System.out.println(m);

}

//本类中的方法，没有父类的方法

Method[] declaredMethods = aClass.getDeclaredMethods();

for (Method m:declaredMethods

) {

System.out.println(m);

}

Method gege = aClass.getMethod("gege",String.class);

//获取gege方法的权限修饰符

System.out.println(Modifier.toString(gege.getModifiers()));

//获取gege方法的返回值类型

System.out.println(gege.getReturnType());

//设置gege的参数值

Object o = aClass.newInstance();

gege.invoke(o,"aa");

}

}

5.反射之获取字段

public class Test6 {

public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException, IllegalAccessException, InstantiationException {

String string = ResourceBundle.getBundle("phone").getString("myphone");

Class> aClass = Class.forName(string);

//只能调用public 字段,但是能得到父类的字段

Field[] fields = aClass.getFields();

for (Field f:fields

) {

System.out.println(f.getName());

}

//只能调用public 字段，只能得到本类中的字段

Field[] declaredFields = aClass.getDeclaredFields();

for (Field f:declaredFields

) {

System.out.println(f.getName());

}

//获取某一字段的数据类型

Field name = aClass.getField("name");

String simpleName = name.getType().getSimpleName();

System.out.println(simpleName);

name.setAccessible(true);

Object o = aClass.newInstance();

name.set(o,"华为");

System.out.println(name.get(o));

}

}

总结

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