public class Main {
public static void main(String[] args) throws IllegalAccessException, InstantiationException {
Class<Person> clazz = Person.class;
Person person = clazz.newInstance();
System.out.println(person instanceof Person); // true
}
}
class Person {
private Integer age;
private String name;
public Person() {
}
}
public class Main {
public static void main(String[] args) throws IllegalAccessException, InstantiationException, ClassNotFoundException {
Class<?> clazz = Class.forName("com.best.test.Person");
Person person = (Person) clazz.newInstance();
System.out.println(person instanceof Person); // true
}
}
class Person {
private Integer age;
private String name;
public Person() {
}
}
public class Main {
public static void main(String[] args) throws IllegalAccessException, InstantiationException{
Person person = new Person();
Class<? extends Person> clazz = person.getClass();
Person person1 = clazz.newInstance();
System.out.println(person1 instanceof Person); // true
}
}
class Person {
private Integer age;
private String name;
public Person() {
}
}
通过类对象的getConstructor()或getDeclaredConstructor()方法获得构造器（Constructor）对象并调用其newInstance()方法创建对象，适用于无参和有参构造方法。
public class Main {
public static void main(String[] args) throws IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException {
Class<Person> clazz = Person.class;
Constructor<Person> ctor = clazz.getConstructor(Integer.class, String.class);
Person person = ctor.newInstance(26, "jak");
System.out.println(person instanceof Person); // true
}
}
class Person {
private Integer age;
private String name;
public Person(Integer age, String name) {
this.age = age;
this.name = name;
}
}
public class Main {
public static void main(String[] args) throws IllegalAccessException, InstantiationException, NoSuchMethodException, InvocationTargetException {
Class<Person> clazz = Person.class;
Constructor<Person> ctor = clazz.getDeclaredConstructor(String.class);
Person person = ctor.newInstance("jak");
System.out.println(person instanceof Person); // true
}
}
class Person {
private Integer age;
private String name;
public Person(Integer age, String name) {
this.age = age;
this.name = name;
}
public Person(String name) {
this.name = name;
}
}
getDeclaredConstructor(Class<?>... parameterTypes)
这个方法会返回指定参数类型的所有构造器，包括public的和非public的，当然也包括private的。getDeclaredConstructors()的返回结果就没有参数类型的过滤了。
再来看getConstructor(Class<?>... parameterTypes)
这个方法返回的是上面那个方法返回结果的子集，只返回指定参数类型访问权限是public的构造器。getConstructors()的返回结果同样也没有参数类型的过滤。
