Question

I was analyzing a open-source game code and i don’t understand setDefaultSpecialChars() method and setDefaultSmallAlphabet(). These statements fontCharTable[':']=1 + indexOf_Point; and fontCharTable['a'+i] = indexOf_a + i; are new to me.

 import javax.microedition.midlet.*;
 import javax.microedition.lcdui.*;

public class GFont {


public int[] fontCharTable = new int[256];

public void setFontCharTableDefaults(boolean specialChars) {
    setDefaultSmallAlphabet(0);
    setDefaultBigAlphabet(0);
    setDefaultDigits(27);
    if (specialChars) {
        setDefaultSpecialChars(37);
    }
}

public void setDefaultSpecialChars(int indexOf_Point) {
    fontCharTable['.']=0 + indexOf_Point;
    fontCharTable[':']=1 + indexOf_Point;
    fontCharTable[',']=2 + indexOf_Point;
    fontCharTable[';']=3 + indexOf_Point;
    fontCharTable['?']=4 + indexOf_Point;
    fontCharTable['!']=5 + indexOf_Point;
    fontCharTable['(']=6 + indexOf_Point;
    fontCharTable[')']=7  + indexOf_Point;
    fontCharTable['+']=8 + indexOf_Point;
    fontCharTable['-']=9 + indexOf_Point;
    fontCharTable['*']=10 + indexOf_Point;
    fontCharTable['/']=11 + indexOf_Point;
    fontCharTable['=']=12  + indexOf_Point;
    fontCharTable['\'']=13 + indexOf_Point;
    fontCharTable['_']=14 + indexOf_Point;
    fontCharTable['\\']=15 + indexOf_Point;
    fontCharTable['#']=16 + indexOf_Point;
    fontCharTable['[']=17 + indexOf_Point;
    fontCharTable[']']=18 + indexOf_Point;
    fontCharTable['@']=19 + indexOf_Point;
    fontCharTable['ä']=20 + indexOf_Point;
    fontCharTable['ö']=21 + indexOf_Point;
    fontCharTable['ü']=22 + indexOf_Point;
    fontCharTable['Ä']=fontCharTable['ä'];
    fontCharTable['Ö']=fontCharTable['ö'];
    fontCharTable['Ü']=fontCharTable['ü'];
}


public void setDefaultSmallAlphabet(int indexOf_a) {
    for (i=0; i<26; i++) {
        fontCharTable['a'+i] = indexOf_a + i;
    }
}


}

Answer 1

It’s just a normal array element assignment expression – but using the implicit conversion from char to int. So take this:

fontCharTable['+']=8 + indexOf_Point;

Now consider it as:

char indexAsChar = '+';
int indexAsInt = indexAsChar; // Use implicit conversion
fontCharTable[indexAsInt] = 8 + indexOf_Point;

Is that now clearer?

Likewise this:

for (i=0; i<26; i++) {
    fontCharTable['a'+i] = indexOf_a + i;
}

could be written as:

for (i=0; i<26; i++) {
    int a = 'a';
    int index = a + i'
    fontCharTable[index] = indexOf_a + i;
}