Question

The below code is extraction from a Java program. The program code is very big so I am just posting the needed part. In the code, what does the if (i == 2) do? What does it check, and how can it check for 2?

panel.setLayout(new GridLayout(5, 4, 5, 5));

String[] buttons = {
    "Cls", "Bck", "", "Close", "7", "8", "9", "/", "4", 
    "5", "6", "*", "1", "2", "3", "-", "0", ".", "=", "+"
};


for (int i = 0; i < buttons.length; i++) {

    if (i == 2) 
        panel.add(new JLabel(buttons[i]));
    else 
        panel.add(new JButton(buttons[i]));
}

Answer 1

Given the line:

for (int i = 0; i < buttons.length; i++) {

The for statement creates the variable i at value 0. Then it runs the code between { and } one time for each value in the array buttons (a list structure), increasing the variable i for each time.

The first time through, the line if (i == 2) will fail, because i is still 0, and then calling the code after the elsestatement. This adds a button with the text Cls.

The third time through the code the variable i will be 2 (because it started at zero), and then it will run the line after if (i == 2) – because that is what it does.

It will then add a an empty label (the third entry in the array buttons, arrays start at 0 for the first position.) instead of a button.

I suggest having a look at the Java tutorials for more information on the language and structures of it. 🙂