使用反射来加载类

    Properties properties=new Properties();
        BufferedReader read=new BufferedReader(new FileReader("class.txt"));
        properties.load(read);
        String className = properties.getProperty("className");
        String method = properties.getProperty("method");
        System.out.println("-------获取类对象文件--------");
        Class   c = Class.forName(className);
        System.out.println(c);
        System.out.println("-------获取构造方法--------");
        Constructor con = c.getDeclaredConstructor();
        System.out.println(con);
        System.out.println("-------获取成员方法--------");
        Method method5 = c.getMethod("method5", String.class);
        System.out.println(method5);
        System.out.println("-------实例化对象--------");
        Object obj = con.newInstance();
        System.out.println(obj);
        System.out.println("-------执行方法--------");
        Object invoke = method5.invoke(obj, "你好");
        System.out.println("-------方法返回值--------");
        System.out.println(invoke);
输出：
-------获取类对象文件--------
class cn.User
-------获取构造方法--------
public cn.User()
-------获取成员方法--------
public java.lang.String cn.User.method5(java.lang.String)
-------实例化对象--------
Person [name=null, id=0, password=null]
-------执行方法--------
show5:你好
-------方法返回值--------
你好

class.txt

className=cn.User
methodName=method5

User

public class User {
    private String name;
    int id;
    public String password;

    public User() {
    }

    private User(String name) {
        this.name = name;
    }

    User(String name, int id) {
        this.name = name;
        this.id = id;
    }

    public User(String name, int id, String password) {
        this.name = name;
        this.id = id;
        this.password = password;
    }



    public void method(String s) {
        System.out.println("method ");
    }

    public void method2(String s) {
        System.out.println("method2");
    }

    private void method3() {
        System.out.println("method3");
    }

    public void method4() {
        System.out.println("show4");
    }
    public String method5(String s) {
        System.out.println("show5:"+s);
        return s;
    }
    @Override
    public String toString() {
        return "Person [name=" + name + ", id=" + id + ", password=" + password
                + "]";
    }

}