How to check if an array is empty

Question

I have written a program where if the array set is let s say  1  3  6  7  12   it will return its minimum gap between two numbers  In other words  it will first find the differences between 3 and 1  6 and 3  7 and 6  and 12 and 7  After their differences are achieved  it will return the least difference  in our case 1  since 6-7 1  If we were given an array set of  60   for example  the program will return 0  Now if we had an array set of     where nothing is inside  it will return 0 as well  However  I can t get my program to return a 0  It throws an exception  What did I miss  How should I solve this problem  Here is my program so far   public static void main String   args        int   numberSet    1  3  6  7  12         int   numberSet           System out println minGap numberSet             public static int minGap int   numberSet        int   differenceArray   new int numberSet length-1       int smallestNum   0      if  numberSet length  lt  2            return 0            else           for int i   0  i  lt  numberSet length-1  i                  differenceArray i    numberSet i 1  - numberSet i                             Arrays sort differenceArray           smallestNum   differenceArray 0           return smallestNum            Thanks in advance

User · Accepted Answer

Your test    if  numberSet length  lt  2        return 0      should be done before you allocate an array of that length in the below statement   int   differenceArray   new int numberSet length-1     else you are already creating an array of size -1  when the numberSet length   0  That is quite odd  So  move your if statement as the first statement in your method

User · Answer

you may use yourArray length to findout number of elements in an array   Make sure yourArray is not null before doing yourArray length  otherwise you will end up with NullPointerException

User · Answer

Your problem is that you are NOT testing the length of the array until it is too late   But I just want to point out that the way to solve this problem is to READ THE STACK TRACE   The exception message will clearly tell you are trying to create an array with length -1  and the trace will tell you exactly which line of your code is doing this   The rest is simple logic     working back to why the length you are using is -1

User · Answer

To check array is null   int arr     null  if  arr    null     System out println  array is null        To check array is empty   arr   new int 0   if  arr length    0     System out println  array is empty

[java] How to check if an array is empty?

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