Tweaked code to avoid overflow entirely.

src/io/nayuki/fastqrcodegen/QrCode.java

@@ -206,14 +206,12 @@ public final class QrCode {
 	public String toSvgString(int border) {
 		if (border < 0)
 			throw new IllegalArgumentException("Border must be non-negative");
-		if (size + border * 2L > Integer.MAX_VALUE)
-			throw new IllegalArgumentException("Border too large");
-		
+		long brd = border;
 		StringBuilder sb = new StringBuilder()
 			.append("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n")
 			.append("<!DOCTYPE svg PUBLIC \"-//W3C//DTD SVG 1.1//EN\" \"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd\">\n")
 			.append(String.format("<svg xmlns=\"http://www.w3.org/2000/svg\" version=\"1.1\" viewBox=\"0 0 %1$d %1$d\" stroke=\"none\">\n",
-				size + border * 2))
+				size + brd * 2))
 			.append("\t<rect width=\"100%\" height=\"100%\" fill=\"#FFFFFF\"/>\n")
 			.append("\t<path d=\"");
 		boolean head = true;
@@ -224,7 +222,7 @@ public final class QrCode {
 						head = false;
 					else
 						sb.append(" ");
-					sb.append(String.format("M%d,%dh1v1h-1z", x + border, y + border));
+					sb.append(String.format("M%d,%dh1v1h-1z", x + brd, y + brd));
 				}
 			}
 		}