java 捕捉null异常,在Java中捕获nullpointerexception
I tried using try-catch block to catch NullPointerException but still the following program is giving errors. Am I doing something wrong or is there any other way to catch NullPointerException in the following program. Any help is highly appreciated.
public class Circular_or_not
{
/**
* @param args
*/
public static void main(String[] args)
{
// TODO Auto-generated method stub
try
{
LinkedListNode[] nodes = new LinkedListNode[10];
for (int i = 0; i < 10; i++)
{
nodes[i] = new LinkedListNode(i, null, i > 0 ? nodes[i - 1] : null);
}
// Create loop;
// nodes[9].next = nodes[3];
Boolean abc= Check_Circular(nodes[0]);
System.out.print(abc);
}
catch(NullPointerException e)
{
System.out.print("NullPointerException caught");
}
}
public static boolean Check_Circular(LinkedListNode head)
{
LinkedListNode n1 = head;
LinkedListNode n2 = head;
// Find meeting point
while (n2.next != null)
{
n1 = n1.next;
n2 = n2.next.next;
if (n1 == n2)
{
return true;
}
}
return false;
}
}
解决方案
NullPointerException is a run-time exception which is not recommended to catch it, but instead avoid it:
if(someValriable != null) someValriable.doSomething();
else
{
// do something else
}
I tried using try-catch block to catch NullPointerException but still the following program is giving errors. Am I doing something wrong or is there any other way to catch NullPointerException in the following program. Any help is highly appreciated. public class Circular_or_not { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub try { LinkedListNode[] nodes = new LinkedListNode[10]; for (int i = 0; i < 10; i++) { nodes[i] = new LinkedListNode(i, null, i > 0 ? nodes[i - 1] : null); } // Create loop; // nodes[9].next = nodes[3]; Boolean abc= Check_Circular(nodes[0]); System.out.print(abc); } catch(NullPointerException e) { System.out.print("NullPointerException caught"); } } public static boolean Check_Circular(LinkedListNode head) { LinkedListNode n1 = head; LinkedListNode n2 = head; // Find meeting point while (n2.next != null) { n1 = n1.next; n2 = n2.next.next; if (n1 == n2) { return true; } } return false; } } 解决方案 NullPointerException is a run-time exception which is not recommended to catch it, but instead avoid it: if(someValriable != null) someValriable.doSomething(); else { // do something else }