In net.jforum.util.preferences.VariableExpander Why does jforum consider whether the value of fIndex

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In net.jforum.util.preferences.VariableExpander
Why does jforum consider whether the value of fIndex equals 0 or not?

while (fIndex > -1) {
			//?????????
			int lIndex = sb.indexOf(this.post);
			
			int start = fIndex + this.pre.length();
			
			if (fIndex == 0) {
				String varName = sb.substring(start, start + lIndex - this.pre.length());
				sb.replace(fIndex, fIndex + lIndex + 1, this.variables.getVariableValue(varName));
			}
			else {
				String varName = sb.substring(start, lIndex);
				sb.replace(fIndex, lIndex + 1, this.variables.getVariableValue(varName));
			}
			
			fIndex = sb.indexOf(this.pre);
		}

I can get didentical result when I comment

if (fIndex == 0) {
				String varName = sb.substring(start, start + lIndex - this.pre.length());
				sb.replace(fIndex, fIndex + lIndex + 1, this.variables.getVariableValue(varName));
			}
			else {

[originally posted on jforum.net by musicbox95351]