Question

I want to get previous value of variable (gmtHourPrev), so I do as following. After change time for testing purpose, I saw the value of gmtHourPrev always equal gmtHour and can’t get previous value of it. What am I doing wrong here ? Thanks

private int gmtHour;
private int gmtHourPrev;

public int getHour() {
    return gmtHour;
}    
public void setGmtHour(int gHour) {
    this.gmtHourPrev = this.gmtHour;
    this.gmtHour = gHour;
}    
public int getGmtHourPrev() {
    return gmtHourPrev;
}

public String getGmtHourInfo() {
    gmtHour = Calendar.HOUR;
    setGmtHour(gmtHour);
    if (isOK() == true) {
       return gmtHour;
    }
    else {
       return getGmtHourPrev();
    }
}

Answer 1

Look at this:

gmtHour = Calendar.HOUR;
setGmtHour(gmtHour);

Aside from the fact that Calendar.HOUR probably isn’t what you think it is (that’s a constant) you’re effectively setting the variable twice. The above code is equivalent to:

gmtHour = Calendar.HOUR;
gmtHourPrev = gmtHour;
gmtHour = gmtHour;

That’s equivalent to:

gmtHour = Calendar.HOUR;
gmtHourPrev = Calendar.HOUR;

You need to only set it once, e.g. just calling

setGmtHour(Calendar.HOUR);

Again though, that value almost certainly isn’t what you want it to be…

You probably want:

setGmtHour(calendar.get(Calendar.HOUR));

for some instance of Calendar.

Oh, and trying to return an int from a method declared to return String isn’t a great idea either…