JAVA使用反射机制获取类的对象和运行时类的完整结构-----JAVA入门基础教程
import org.junit.jupiter.api.Test; import java.lang.annotation.Annotation; import java.lang.reflect.Field; import java.lang.reflect.Method; import java.lang.reflect.Modifier; public class NewInstanceTest { @Test public void Test() throws Exception { Class c = Person.class; //通过Class的实例调用newInstance()方法即可创建类的实例对象 Person p = (Person)c.newInstance(); System.out.println(p); //要想创建对象成功,需要运行时类提供一个空参的构造器,其权限要足够,才能使用newInstance方法 //JDK9以后我们用Constructor类调用newInstance //只能获取运行时类及父类的public权限的属性 Field[] fields = c.getFields(); for(Field f : fields) { System.out.println(f); } //获取运行时类的所有的属性 System.out.println(); fields = c.getDeclaredFields(); for(Field field : fields) { //获取权限修饰符号 int m = field.getModifiers(); System.out.print(Modifier.toString((m))); //获取数据类型 Class type = field.getType(); System.out.print(type.getName()); //变量名 String string = field.getName(); System.out.print(string); System.out.println(); System.out.println(field); } } public static void main(String[] args) { Class c = Person.class; Method[] d = c.getDeclaredMethods(); for(Method m : d) { //获取方法注解信息 Annotation[] annotations = m.getAnnotations(); for(Annotation annotation : annotations) { System.out.println(annotation); } //权限修饰符 System.out.println(Modifier.toString(m.getModifiers())); //返回值类型 System.out.println(m.getReturnType().getName()); //形参列表 Class[] parameter = m.getParameterTypes(); if(!(parameter == null && parameter.length == 0)) { for (int i = 0; i < parameter.length; i++) { if(i == parameter.length - 1) { System.out.print(parameter[i].getName()); break; } System.out.print(parameter[i].getName()); } } //抛出的异常 Class[] e = m.getExceptionTypes(); if(e.length > 0) { System.out.println("throws"); for(int i = 0;i < e.length;i++) { if(i == e.length - 1) { System.out.println(e[i].getName()); break; } System.out.println(e[i].getName()); } } System.out.println(); } } }import org.junit.jupiter.api.Test;
import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
public class NewInstanceTest
{
@Test
public void Test() throws Exception
{
Class c = Person.class;
//通过Class的实例调用newInstance()方法即可创建类的实例对象
Person p = (Person)c.newInstance();
System.out.println(p);
//要想创建对象成功,需要运行时类提供一个空参的构造器,其权限要足够,才能使用newInstance方法
//JDK9以后我们用Constructor类调用newInstance
//只能获取运行时类及父类的public权限的属性
Field[] fields = c.getFields();
for(Field f : fields)
{
System.out.println(f);
}
//获取运行时类的所有的属性
System.out.println();
fields = c.getDeclaredFields();
for(Field field : fields)
{
//获取权限修饰符号
int m = field.getModifiers();
System.out.print(Modifier.toString((m)));
//获取数据类型
Class type = field.getType();
System.out.print(type.getName());
//变量名
String string = field.getName();
System.out.print(string);
System.out.println();
System.out.println(field);
}
}
public static void main(String[] args)
{
Class c = Person.class;
Method[] d = c.getDeclaredMethods();
for(Method m : d)
{
//获取方法注解信息
Annotation[] annotations = m.getAnnotations();
for(Annotation annotation : annotations)
{
System.out.println(annotation);
}
//权限修饰符
System.out.println(Modifier.toString(m.getModifiers()));
//返回值类型
System.out.println(m.getReturnType().getName());
//形参列表
Class[] parameter = m.getParameterTypes();
if(!(parameter == null && parameter.length == 0))
{
for (int i = 0; i < parameter.length; i++)
{
if(i == parameter.length - 1)
{
System.out.print(parameter[i].getName());
break;
}
System.out.print(parameter[i].getName());
}
}
//抛出的异常
Class[] e = m.getExceptionTypes();
if(e.length > 0)
{
System.out.println("throws");
for(int i = 0;i < e.length;i++)
{
if(i == e.length - 1)
{
System.out.println(e[i].getName());
break;
}
System.out.println(e[i].getName());
}
}
System.out.println();
}
}
}
import java.lang.reflect.ParameterizedType; import java.lang.reflect.Type; public class OtherTest { public static void main(String[] args) throws Exception { //获取父类 Class c = Class.forName("Person"); Class s = c.getSuperclass(); System.out.println(s); //获取带泛型的父类 Type ss = c.getGenericSuperclass(); System.out.println(ss); //获取运行时类实现的接口 Type[] types = c.getInterfaces(); for(Type type : types) { System.out.println(type.getTypeName()); } //获取运行时类所在的包 System.out.println(c.getPackageName()); System.out.println(c.getPackage().toString()); //获取运行时类的父类的泛型,Type是一个接口,Class实现了此接口 ParameterizedType parameterizedType = (ParameterizedType) ss; Type[] a = parameterizedType.getActualTypeArguments(); for(Type type : a) { System.out.println(((Class)type).getName()); } //如果父类是带泛型的,则可以强转为ParameterizedType类型,调用getActualTypeArguments()得到数组 } }import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
public class OtherTest
{
public static void main(String[] args) throws Exception
{
//获取父类
Class c = Class.forName("Person");
Class s = c.getSuperclass();
System.out.println(s);
//获取带泛型的父类
Type ss = c.getGenericSuperclass();
System.out.println(ss);
//获取运行时类实现的接口
Type[] types = c.getInterfaces();
for(Type type : types)
{
System.out.println(type.getTypeName());
}
//获取运行时类所在的包
System.out.println(c.getPackageName());
System.out.println(c.getPackage().toString());
//获取运行时类的父类的泛型,Type是一个接口,Class实现了此接口
ParameterizedType parameterizedType = (ParameterizedType) ss;
Type[] a = parameterizedType.getActualTypeArguments();
for(Type type : a)
{
System.out.println(((Class)type).getName());
}
//如果父类是带泛型的,则可以强转为ParameterizedType类型,调用getActualTypeArguments()得到数组
}
}
public class Creature{ protected boolean gender; public int id; public void breath() { System.out.println("Breath"); } private void info() { System.out.println("info"); } } public class Creature
{
protected boolean gender;
public int id;
public void breath()
{
System.out.println("Breath");
}
private void info()
{
System.out.println("info");
}
}
public interface MyInterface { void method(); }public interface MyInterface
{
void method();
}
public class Person extends Creatureimplements Comparable ,MyInterface { private String name; public int age = 1; private static String info; public Person() { System.out.println("Person"); } protected Person(int age) { this.age = age; } private Person(String name,int age) { this.age = age; this.name = name; } public void show() throws RuntimeException,ClassNotFoundException { System.out.println("是个人"); } private String showNation(String nation,int age) { System.out.println("nation"); return nation + age; } @Override public String toString() { return "Person{" + "name='" + name + '\'' + ", age=" + age + '}'; } public int compareTo(Person person) { return 0; } public static void showInfo() { System.out.println("人"); } @Override public void method() { } } public class Person extends Creature
implements Comparable ,MyInterface
{
private String name;
public int age = 1;
private static String info;
public Person()
{
System.out.println("Person");
}
protected Person(int age)
{
this.age = age;
}
private Person(String name,int age)
{
this.age = age;
this.name = name;
}
public void show() throws RuntimeException,ClassNotFoundException
{
System.out.println("是个人");
}
private String showNation(String nation,int age)
{
System.out.println("nation");
return nation + age;
}
@Override
public String toString()
{
return "Person{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
public int compareTo(Person person)
{
return 0;
}
public static void showInfo()
{
System.out.println("人");
}
@Override
public void method() {
}
}