java关于调用方法的汇总

class A{
  //静态方法,可以使用类名点方法名直接调用,比如A.sayHello() 
  public static void sayHello(){
    System.out.println("静态方法输出成功:Hello");
  }
  //实例方法,必须创建类的实例,然后才能调用A a = new A(); a.sayWorld();
  public void sayWorld(){
    System.out.println("实例方法输出成功:World");
  }
}
 
public class MyDemo {  
  public static void main(String[] args) {
    A a = null;
    try{
      a.sayHello();//调用静态方法
    }catch(NullPointerException e){
      System.out.println("调用静态方法出现了空指针异常");
    }
    try{
      a.sayWorld();//调用实例方法
    }catch(NullPointerException e){
      System.out.println("调用实例方法出现了空指针异常");
    }
  }
}

import java.lang.reflect.Method; 

public class DongTai { 
  public static void main(String[] args) { 
    try { 
      System.out.println("调用Math类的静态方法sin()"); 
      Method sin = Math.class.getDeclaredMethod("sin", Double.TYPE); 
      Double sin1 = (Double) sin.invoke(null, new Integer(1)); 
      System.out.println("1的正弦值是：" + sin1); 
      System.out.println("调用String类的非静态方法equals()"); 
      Method equals = String.class.getDeclaredMethod("equals", Object.class); 
      Boolean mrsoft = (Boolean) equals.invoke(new String("明日科技"), "明日科技"); 
      System.out.println("字符串是否是明日科技：" + mrsoft); 
    } catch (Exception e) { 
      e.printStackTrace(); 
    } 
  } 
}