请问这些类怎么用？（NullPointerException、ClassCastException、NegativeArraySizeException、ArrayIndexOutofBoundsException）？

Question

这个题目是什么意思呢？
编写一个程序，在main方法中，输入语句，根据不同的错误捕获相应的异常。（NullPointerException、ClassCastException、NegativeArraySizeException、ArrayIndexOutofBoundsException）

Answer 1

import java.*;
import java.lang.*;
import java.util.*;
class test  
{
public static void main (String[] args) throws NullPointerException,ClassCastException,NegativeArraySizeException,ArrayIndexOutOfBoundsException
{
try
{
Integer i = null;
System.out.println(i.toString());
}
catch (NullPointerException ex1)
{
System.out.println("NullPointerException");
}

try
{
Object i2 = 123;
int[] arr = (int[])i2;
}
catch (ClassCastException ex2)
{
System.out.println("ClassCastException");
}

try
{
int[] arr2 = new int[-1];
}
catch (NegativeArraySizeException ex3)
{
System.out.println("NegativeArraySizeException");
}

try
{
int[] arr3 = new int[10];
System.out.println(arr3[11]);
}
catch (ArrayIndexOutOfBoundsException ex4)
{
System.out.println("ArrayIndexOutOfBoundsException");
}
}
}