This test to display text field in a conditional statement

Question

Still a newbie! I want to test the display for my calc app so that you can't add zeros to the display's default zero i.e. if the display is "0" and I keep pressing the "0" key , it won't get appended to the first zero.
if(nonum == "0") doesn't seem to work
public boolean processKey (int keyCode) {
String newnum = curnum;
String nonum = display.getText();
if (keyCode >= 0 && keyCode <= 9){
if(nonum == "0"){
newnum = Integer.toString(keyCode);
System.out.println("display reads "+nonum);
}else{
newnum += Integer.toString(keyCode);
else if (keyCode == POINT)
newnum += ".";
try {
Double.parseDouble(newnum);
curnum = newnum;
System.out.println("newnum = " + newnum);
System.out.println("curnum = " + curnum);
return true; }
catch (NumberFormatException nfx) {
return false; }

Answer 1

Since you are storing the number as an 'int' and then converting that int to a String for display, then you shouldn't expect 0's to be added on if the number is currently 0:
1) curnum = 0
2) 0 key is pressed
3) curnum = curnum * 10 + 0 = 0 * 10 + 0 = 0
A real calculator wouldn't keep appending 0's... at least, not a simple calculator comparable to the one you are writing. If you want to append 0's, try this:
- Keep a count of the number of 0's pressed.
- If curnum is changed to 0 (by pressing clear, for example, or turning on the calculator), reset the zero count to 1.
- Each time the '0' key is pressed, if curnum is 0, then increment the '0' count.
- When you update your display, use the following logic: if curnum is 0, then display the number of 0's specified in the zero count, otherwise just display the value of curnum.
Jason