用反射调用类里的方法
public class Calculator{ public double add(double score1,double score2){ return score1 + score2; } public void print(){ System.out.println("OK"); } public static double mul(double score1,double score2){ return score1 * score2; }} |
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
|
public class CalculatorTest { public static void main(String[] args) throws Exception { //通过类的.class属性获取 Class<Calculator> clz = Calculator.class; //或者通过类的完整路径获取,这个方法由于不能确定传入的路径是否正确,这个方法会抛ClassNotFoundException// Class<Calculator> clz = Class.forName("test.Calculator"); //或者new一个实例,然后通过实例的getClass()方法获取// Calculator s = new Calculator();// Class<Calculator> clz = s.getClass(); //1. 获取类中带有方法签名的mul方法,getMethod第一个参数为方法名,第二个参数为mul的参数类型数组 Method method = clz.getMethod("mul", new Class[]{double.class,double.class}); //invoke 方法的第一个参数是被调用的对象,这里是静态方法故为null,第二个参数为给将被调用的方法传入的参数 Object result = method.invoke(null, new Object[]{2.0,2.5}); //如果方法mul是私有的private方法,按照上面的方法去调用则会产生异常NoSuchMethodException,这时必须改变其访问属性 //method.setAccessible(true);//私有的方法通过发射可以修改其访问权限 System.out.println(result);//结果为5.0 //2. 获取类中的非静态方法 Method method_2 = clz.getMethod("add", new Class[]{double.class,double.class}); //这是实例方法必须在一个对象上执行 Object result_2 = method_2.invoke(new Calculator(), new Object[]{2.0,2.5}); System.out.println(result_2);//4.5 //3. 获取没有方法签名的方法print Method method_3 = clz.getMethod("print", new Class[]{}); Object result_3 = method_3.invoke(new Calculator(), null);//result_3为null,该方法不返回结果 }} |
package thread;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
public class Teacher {
public String getName(String name, String address, Integer age) {
return name + "是一名人民教师,在"+address+","+age+"岁";
}
public static void main(String[] args) {
try {
Class<?> clazz = Class.forName("thread.Teacher");
Method method = clazz.getMethod("getName", String.class, String.class, Integer.class);
Object obj = method.invoke(clazz.newInstance(), "李梅","上海", 21);
System.out.println(obj);
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (NoSuchMethodException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SecurityException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InvocationTargetException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InstantiationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
