反射java

import java.lang.reflect.Constructor;

class Person {

    public Person() {

    }

    public Person(String name) {
        this.name = name;
    }

    public Person(int age) {
        this.age = age;
    }

    public Person(String name, int age) {
        this.age = age;
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    @Override
    public String toString() {
        return "[" + this.name + "  " + this.age + "]";
    }

    private String name;
    private int age;
}

public class reflection {
    public static void main(String[] args) {
        Class<?> demo = null;
        try {
            demo = Class.forName("reflectAndGeneric.Person");
        } catch (Exception e) {
            e.printStackTrace();
        }
        Person per1 = null;
        Person per2 = null;
        Person per3 = null;
        Person per4 = null;
        // 取得全部的构造函数
        Constructor<?> cons[] = demo.getConstructors();
        try {
            for (int i = 0; i < cons.length; i++) {
                System.out.println(cons[i]);
            }
            per1=(Person)cons[2].newInstance();
            per2=(Person)cons[3].newInstance("Rollen");
            per3=(Person)cons[1].newInstance(20);
            per4=(Person)cons[0].newInstance("Rollen",20);
        } catch (Exception e) {
            e.printStackTrace();
        }
        System.out.println(per1);
        System.out.println(per2);
        System.out.println(per3);
        System.out.println(per4);
    }
}

getConstructors()得到的构造器顺序好奇怪，和定义的顺序不同。把cons[]数组的下标改成对应的构造器顺序。

输出结果：

public Person(java.lang.String,int)
public Person(int)
public Person()
public Person(java.lang.String)
[null  0]
[Rollen  0]
[null  20]
[Rollen  20]

2.读取properties文件属性+反射工厂

import java.io.*;
import java.util.*;

interface fruit {
    public abstract void eat();
}

class Apple implements fruit {
    public void eat() {
        System.out.println("Apple");
    }
}

class Orange implements fruit {
    public void eat() {
        System.out.println("Orange");
    }
}

// 操作属性文件类
class init {
    public static Properties getPro() throws FileNotFoundException, IOException {
        Properties pro = new Properties();
        File f = new File("fruit.properties");//地址写全
        if (f.exists()) {
            pro.load(new FileInputStream(f));
        } else {
            pro.setProperty("apple", "reflectAndGeneric.Apple");
            pro.setProperty("orange", "reflectAndGeneric.Orange");
            pro.store(new FileOutputStream(f), "FRUIT CLASS");
        }
        return pro;
    }
}

class Factory {
    public static fruit getInstance(String ClassName) {
        fruit f = null;
        try {
            f = (fruit) Class.forName(ClassName).newInstance();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return f;
    }
}

// 结合属性文件的反射工厂类。
public class reflectionFactory {

    public static void main(String[] a) throws FileNotFoundException, IOException {
        Properties pro = init.getPro();
        fruit f = Factory.getInstance(pro.getProperty("apple"));
        if (f != null) {
            f.eat();
        }
    }
}

 输出结果：

Apple