爪哇国新游记之十----异常初相识

import java.util.ArrayList;
import java.util.List;


public class A{
    private int[] arr=new int[3];
    private List<String> ls;
    
    public A(){
        ls=new ArrayList<String>();
        ls.add("12");
    }
    
    public int getArrValue(int i){
        return arr[i];
    }
    
    public String getListValue(int i){
        return ls.get(i);
    }
    
    public static void main(String[] args){
        try{
            A a=new A();
            int v1=a.getArrValue(0);
            String v2=a.getListValue(0);
            
            throw new Exception("自定义异常发生");
        }catch(java.lang.NullPointerException e){
            System.out.println("a未实例化或A.ls未实例化");
        }catch(java.lang.IndexOutOfBoundsException e){
            System.out.println("A.arr取值下标越界或A.ls取值下标越界");
        }catch(Exception e){
            e.printStackTrace();
        }
    }
}