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
publicclassPhoneimplementsList{
publicdoubleprice;
publicStringname;
publicPhone(){
}
publicPhone(doubleprice,Stringname){
this.price=price;
this.name=name;
}
publicdoublegetPrice(){
returnprice;
}
publicvoidgege(Stringh){
System.out.println("gege的"+h);
}
publicvoidsetPrice(doubleprice){
this.price=price;
}
publicStringgetName(){
returnname;
}
publicvoidsetName(Stringname){
this.name=name;
}
@Override
publicStringtoString(){
return"Phone{"+
"price="+price+
",name='"+name+'\''+
'}';
}
@Override
publicintsize(){
return0;
}
@Override
publicbooleanisEmpty(){
returnfalse;
}
@Override
publicbooleancontains(Objecto){
returnfalse;
}
@Override
publicIteratoriterator(){
returnnull;
}
@Override
publicObject[]toArray(){
returnnewObject[0];
}
@Override
publicbooleanadd(Objecto){
returnfalse;
}
@Override
publicbooleanremove(Objecto){
returnfalse;
}
@Override
publicbooleanaddAll(Collectionc){
returnfalse;
}
@Override
publicbooleanaddAll(intindex,Collectionc){
returnfalse;
}
@Override
publicvoidclear(){
}
@Override
publicObjectget(intindex){
returnnull;
}
@Override
publicObjectset(intindex,Objectelement){
returnnull;
}
@Override
publicvoidadd(intindex,Objectelement){
}
@Override
publicObjectremove(intindex){
returnnull;
}
@Override
publicintindexOf(Objecto){
return0;
}
@Override
publicintlastIndexOf(Objecto){
return0;
}
@Override
publicListIteratorlistIterator(){
returnnull;
}
@Override
publicListIteratorlistIterator(intindex){
returnnull;
}
@Override
publicListsubList(intfromIndex,inttoIndex){
returnnull;
}
@Override
publicbooleanretainAll(Collectionc){
returnfalse;
}
@Override
publicbooleanremoveAll(Collectionc){
returnfalse;
}
@Override
publicbooleancontainsAll(Collectionc){
returnfalse;
}
@Override
publicObject[]toArray(Object[]a){
returnnewObject[0];
}
}
1.反射之4种new对象
publicclassTest2{
publicstaticvoidmain(String[]args)throwsIllegalAccessException,InstantiationException,ClassNotFoundException{
//第一种
Phonep=newPhone(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
ClassphoneClass=Phone.class;
Phonephone=phoneClass.newInstance();
phone.setName("华为");
phone.setPrice(3499);
System.out.println(phone);//Phone{price=3499.0,name='华为'}
//第三种
Classaclass=Class.forName("com.demo.bean.Phone");
Phonep2=(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
Stringname=ResourceBundle.getBundle("phone").getString("myphone");
ClassbClass=Class.forName(name);
Phonep3=(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
publicclassTest3{
publicstaticvoidmain(String[]args)throwsClassNotFoundException{
Stringstring=ResourceBundle.getBundle("phone").getString("myphone");
ClassaClass=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
Classsuperclass=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(Classin:interfaces
){
System.out.println(in.getSimpleName());
}
}
}
3.反射之获取空参、有参构造
publicclassTest4{
publicstaticvoidmain(String[]args)throwsClassNotFoundException,IllegalAccessException,InstantiationException,NoSuchMethodException{
Stringstring=ResourceBundle.getBundle("phone").getString("myphone");
ClassaClass=Class.forName(string);
//调用的是无参的构造方法
Phonep1=(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
Constructorconstructor=aClass.getConstructor();
System.out.println(constructor);//publiccom.demo.bean.Phone()
//获得所有的构造方法
Constructor[]constructors=aClass.getConstructors();
for(Constructorc:constructors
){
System.out.println(c);
}
}
}
4.反射之获取方法
publicclassTest5{
publicstaticvoidmain(String[]args)throwsClassNotFoundException,NoSuchMethodException,InstantiationException,IllegalAccessException,InvocationTargetException{
Stringstring=ResourceBundle.getBundle("phone").getString("myphone");
ClassaClass=Class.forName(string);
//包含了父类的方法
Method[]methods=aClass.getMethods();
for(Methodm:methods
){
System.out.println(m);
}
//本类中的方法，没有父类的方法
Method[]declaredMethods=aClass.getDeclaredMethods();
for(Methodm:declaredMethods
){
System.out.println(m);
}
Methodgege=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
Objecto=aClass.newInstance();
gege.invoke(o,"aa");
}
}
5.反射之获取字段
publicclassTest6{
publicstaticvoidmain(String[]args)throwsClassNotFoundException,NoSuchFieldException,IllegalAccessException,InstantiationException{
Stringstring=ResourceBundle.getBundle("phone").getString("myphone");
ClassaClass=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(Fieldf: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(Fieldf:declaredFields
){
System.out.println(f.getName());
}
//获取某一字段的数据类型
Fieldname=aClass.getField("name");
StringsimpleName=name.getType().getSimpleName();
System.out.println(simpleName);
name.setAccessible(true);
Objecto=aClass.newInstance();
name.set(o,"华为");
System.out.println(name.get(o));
}
}
总结
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