Similar methods using loops

Question

Is it recommended to combine two similar methods into one?

public void initialize_board(){
    for(int y = 0; y < board.length; y++){
        for(int x = 0; x < board.length; x++){
            if(x == 0)
                board[x][y] = (char)y;
            else
                board[x][y] = '~';
        }
    }
}

public void display_board(){
    for(int y = 0; y < board.length; y++){
        for(int x = 0; x < board.length; x++){
            System.out.print(board[x][y]);
        }
        System.out.print("\n");
    }
}

Answer 1

By the Single Responsibility Principle, they should remain separate methods. Furthermore, initialize_board() should probably be a constructor for a Board class, and display_board() should be its toString().

Answer 2

Not so similar...

Just because the method bodies "look similar" doesn't make them similar. It's better to think in terms of purpose instead. The two methods are for completely different things. They are not similar, and good to be separated.

In functional languages you could use a "walk" method to iterate over all cells of the board and use a callback function to act on each cell. You could emulate that behavior in Java, but the code will get more complex, and I'm not sure it will be worth it in this example.

Robustness

Do you intend to initialize the board more than once in the lifetime of the object? If not (probably), then move the initialization to the constructor.

Writing style

You should use camelCase for naming, for example initializeBoard instead of initialize_board.

---

It's recommended to use braces with ifs, for example:

if (x == 0) {
    board[x][y] = (char)y;
} else {
    board[x][y] = '~';
}

---

It's better to print a newline using println:

System.out.println();
// instead of: System.out.print("\n");

Answer 3

The two methods look similar because at some level they do the same thing : they traverse the board. What is repeated is the code to traverse the data structure. The gang of four identified isolating the traversal behaviour as the iterator pattern.

In object-oriented programming, the iterator pattern is a design pattern in which an iterator is used to traverse a container and access the container's elements.

(from wikipedia)

So you could apply the iterator pattern. If it's really just those two methods, it's probably overkill, but keep it in mind when you find yourself traversing the datastructure in other places as well.

Answer 4

1. I guess this does not do what you really want:

   board[x][y] = (char)y;
   

   It sets the first few ASCII control characters and display_board() shows weird results. I'd try this:

   board[x][y] = Character.forDigit(y, 10); 
   

2. Instead of

   System.out.print("\n");
   

   you should use println() (as @janos already mentioned) but if you want to put a line feed manually you should use

   System.out.print("%n");
   

   instead. %n outputs the correct platform-specific line separator.