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实例讲解Java基础之反射

2019-03-28 10:59 791 查看

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 false;
}
@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<Phone> 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("myphone");
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));
}
}

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