java.lang.NoSuchMethodException

java.lang.NoSuchMethodException: com.gen.entity.User.sayHi()private void com.gen.entity.User.sayHi(java.lang.String)

at java.lang.Class.getDeclaredMethod(Class.java:2130)
at com.gen.test.TestRefelect1.demo01(TestRefelect1.java:27)
at com.gen.test.TestRefelect1.main(TestRefelect1.java:12)

我的代码是这样的：

package com.gen.test;

import java.io.FileInputStream;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Properties;

public class TestRefelect1 {

	public static void main(String[] args) {
		demo01();
	}

	static void demo01() {
		Properties properties = new Properties();
		String name = "D:\\eclipse-workspace\\WEB\\javaPromote\\src\\com\\gen\\test\\class.txt";
		try {
			properties.load(new FileInputStream(name));
			String classname = properties.getProperty("classname");
			String methodname = properties.getProperty("methodname");
			Class<?> forName = Class.forName(classname);
			Method[] declaredMethods = forName.getDeclaredMethods();
			for (Method method : declaredMethods) {
				System.out.println(method);
			}
			Method method = forName.getDeclaredMethod(methodname);
			System.out.println(method);
			method.setAccessible(true);
			method.invoke(forName, "lisi");
		} catch (IOException | ClassNotFoundException | SecurityException
				| IllegalArgumentException | NoSuchMethodException | IllegalAccessException | InvocationTargetException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

	}

}

错误

所有的方法可以遍历出来，但是调用特定的方法却不可以

改正

package com.gen.test;

import java.io.FileInputStream;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Properties;

public class TestRefelect1 {

	public static void main(String[] args) {
		demo01();
	}

	static void demo01() {
		Properties properties = new Properties();
		String name = "D:\\eclipse-workspace\\WEB\\javaPromote\\src\\com\\gen\\test\\class.txt";
		try {
			properties.load(new FileInputStream(name));
			String classname = properties.getProperty("classname");
			String methodname = properties.getProperty("methodname");
			Class<?> forName = Class.forName(classname);
			Method[] declaredMethods = forName.getDeclaredMethods();
			for (Method method : declaredMethods) {
				System.out.println(method);
			}
			Method method = forName.getDeclaredMethod(methodname,String.class);
			System.out.println(method);
			method.setAccessible(true);
			method.invoke(forName, "lisi");
		} catch (IOException | ClassNotFoundException | SecurityException
				| IllegalArgumentException | NoSuchMethodException | IllegalAccessException | InvocationTargetException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

	}

}

主要在27行改正了
Method method = forName.getDeclaredMethod(methodname,String.class);

结果

需要注意的地方

Method Class.getDeclaredMethod(String name, Class... parameterTypes)的作用是获得对象的所有方法

该方法的第一个参数name是要获得方法的名字，第二个参数parameterTypes是按声明顺序标识该方法形参类型，一定要写上（部分教程说这个参数可以省略）。