比较2D字符串数组

Question

I have a method which generates a 2D array of strings, then places them in a ArrayList . I am trying to write a method which take a new 2D array and check it against those already in the array for duplication. This is what I have so far, it should return true for a new solution but it returns false every time. The calling method prints the arrays out and I can see that they are not the same.

public static boolean tester(String[][] b, ArrayList<String[][]> s)
{
    if (s.size() == 1) return true;
    boolean n = true;
    int count;
    int size = b.length * b[0].length;

    for (int i = 0; n && i < s.size() -1; i ++)

    {   
        count = 0;
        for (int j = 0; j < s.get(i).length; j ++)
            for (int k = 0; k < s.get(i)[0].length; k ++)
                if (s.get(i)[j][k].equals(b[j][k])) count ++;
                    if (count == size) n = false;

    }

    return n;
}

Answer 1

Your code can get way simpler by using Arrays.deepEquals :

public static boolean nonDuplicate(ArrayList<String[][]> s, String[][] b){

    for(String[][] e : s){
        if(Arrays.deepEquals(e, b)) return false; //e and b are duplicates
    }

    return true;
}

Your code may be incorrect because you didn't use braces ( {} ) around your for loops. So when you wrote:

    for (int j = 0; j < s.get(i).length; j ++)
        for (int k = 0; k < s.get(i)[0].length; k ++)
            if (s.get(i)[j][k].equals(b[j][k])) count ++;
                if (count == size) n = false;

It was interpreted as:

      for (int j = 0; j < s.get(i).length; j ++){
        for (int k = 0; k < s.get(i)[0].length; k ++){
            if (s.get(i)[j][k].equals(b[j][k])) count ++;
        }
      }

      if (count == size) n = false;

Which was likely (?) not your intention judging by your indentation, though notably white space (including indentation) doesn't mean very much in java aside from separating tokens.

Answer 2

This is how your code gets interpreted by the compiler:

for (int i = 0; n && i < s.size() -1; i ++)
{   
    count = 0;
    for (int j = 0; j < s.get(i).length; j ++) {
        for (int k = 0; k < s.get(i)[0].length; k ++) {           
            if (s.get(i)[j][k].equals(b[j][k])) count ++; 
        }
    }
    if (count == size) n = false;
}

Imho its best to always use { and } to clarify your intentions to the compiler/reader of your code.

I guess what you wanted is this:

for (int i = 0; n && i < s.size() -1; i ++)
{   
    count = 0;
    for (int j = 0; j < s.get(i).length; j ++) {
        for (int k = 0; k < s.get(i)[0].length; k ++) {           
            if (s.get(i)[j][k].equals(b[j][k])) {
                count ++; 
            }
            if (count == size) {
                n = false;
            }
        }
    }
}

But you could also write:

public static boolean tester(String[][] b, ArrayList<String[][]> s)
{ 
    // ..

    for (int i = 0; n && i < s.size() -1; i ++)  {   
        for (int j = 0; j < s.get(i).length; j ++) {
            for (int k = 0; k < s.get(i)[0].length; k ++) {   

                if (s.get(i)[j][k].equals(b[j][k]) == false) {
                    return true; 
                }
            }
        }
    }

    return false;
}