ZC_02_获取Constructor

1、

package reflectionZ;

import java.lang.reflect.Constructor;
import java.lang.reflect.Type;

public class Tzz02
{
    public static void main(String[] args) throws Exception
    {
        // getConstructors() / getConstructor(...)
        
        Class<?> clazz1 = Class.forName("reflectionZ.Cat");
        
        // 1、使用的是 默认的 构造函数
        Object obj01 = clazz1.newInstance();
        
        // 2、通过Class对象来得到构造函数
        Constructor<?> c1 = clazz1.getConstructor(Class.forName("java.lang.String"), int.class);
        Object obj0201 = c1.newInstance("小猫", 6); // 强转
        
        Constructor<?> c2 = clazz1.getConstructor(String[].class);
        String[] foods = {"鱼", "老鼠"};
        Object obj0202 = (Cat)c2.newInstance((Object)foods); // 对象数组foods会被打散
        
        if (obj01.getClass() == clazz1)
            System.out.println("obj01.getClass() == clazz1");
        else
            System.out.println("obj01.getClass() != clazz1");
        if (obj0201.getClass() == clazz1)
            System.out.println("obj01.getClass() == clazz1");
        else
            System.out.println("obj01.getClass() != clazz1");
        if (obj0202.getClass() == clazz1)
            System.out.println("obj01.getClass() == clazz1");
        else
            System.out.println("obj01.getClass() != clazz1");
        
    // *** *** ***
        System.out.println();
        
        int iIdx = 0;
        Constructor<?>[] constructors = clazz1.getConstructors();
        for (Constructor<?> constructor :constructors)
        {
            Type[] types = constructor.getGenericParameterTypes();
            if (types.length == 0)
                System.out.println("["+iIdx+"] ==> 无参构造函数");
            else
            {
                System.out.println("["+iIdx+"] ==> "+types.length+"个参数的 构造函数，参数的类型分别为:");
                for (Type type : types)
                {
                    System.out.println(type);
                }
            }
            System.out.println();
            
            iIdx ++;
        }
    }
}

class Cat
{
    public Cat()
    {}
    public Cat(String _strName, int _iAge)
    {
        System.out.println("Cat --> _strName : "+_strName+" , _iAge : "+_iAge);
    }
    public Cat(String[] _foods)
    {
        if (_foods == null)
            System.out.println("Cat --> _foods is null .");
        else
        {
            for (int i=0; i<_foods.length; i++)
                System.out.println("Cat -->  _foods["+i+"] : "+_foods[i]);
        }
    }
}

 

2、

控制台输出：

Cat --> _strName : 小猫 , _iAge : 6
Cat -->  _foods[0] : 鱼
Cat -->  _foods[1] : 老鼠
obj01.getClass() == clazz1
obj01.getClass() == clazz1
obj01.getClass() == clazz1

[0] ==> 无参构造函数

[1] ==> 2个参数的 构造函数，参数的类型分别为:
class java.lang.String
int

[2] ==> 1个参数的 构造函数，参数的类型分别为:
class [Ljava.lang.String;

 

 

3、