how to check if two dimensional array is empty

Question

how can I check if this two dimentinal array is empty?

this is my code :

 String[][] user = new String[5][3];
 System.out.print(user.length);
 if (user.length == 5 ){
 System.out.print("\n empty");
 }
 for (int j=0; j<3; j++) {
 System.out.print(" " + user[0][j]+ "\n");
 }

and the output is :

5
 empty null null null

Does anyone have an ide about my situation?

• Boris Strandjev: Some code is missing isn't it? How do you get so much output from at most one System.out.println?
• user647772: Define "empty". Do you mean null or ""?
• Sam: I think you don't send complete your code.

Answer 1

You are misunderstanding something in Java I think. When you write :

String[][] user = new String[5][3];
user.length will always be 5 and 
user[0].length = user[1].length = ... = user[5].length = 3

If you want to check if all value in your array are emty you can do something like :

boolean notNull = false;
for(String[] array : user){
 for(String val : array){
 if(val!=null){
 notNull=true;
 break;
 }
 }
}
if(notNull){
 System.out.println("Array not empty)";
}else{
 System.out.println("Array empty");
}

Another solution would be to use Arrays.deepEquals :

String[][] user = new String[5][3];
String[][] emptyReferenceForComparison= new String[5][3];
Arrays.deepEquals(user, emptyReferenceForComparison); // return true

Answer 2

I suggest using Apache Commons Lang3. In this library exist utility for working with arrays. Name of the class is ArrayUtils. For sample:

 String[][] user = new String[5][3];
 for(String[] nestedArray : user)
 if(ArrayUtils.isEmpty(nestedArray))
 System.out.println("Is empty");

Apache Commans Lang3 is good utility. see here for more informations.

Answer 3

Sometimes during competitive programming problems, in order to handle the corner case some code like in the snippet below would be necessary. Just checking matrix.length==0 will not work since it gives only whether the row is empty but there might be a column present in it.

if(matrix.length < 1 || matrix[0].length < 1) {
 return true; //empty
}

• Antares: You're welcome. I am here to help :) Thanks for your feedback.