8353453: URLDecoder should use HexFormat

Reviewed-by: rriggs, jpai

Author: kilink

src/java.base/share/classes/java/net/URLDecoder.java

@@ -29,6 +29,7 @@
 import java.nio.charset.Charset;
 import java.nio.charset.IllegalCharsetNameException;
 import java.nio.charset.UnsupportedCharsetException;
+import java.util.HexFormat;
 import java.util.Objects;
 
 /**
@@ -204,11 +205,7 @@ public static String decode(String s, Charset charset) {
 
                     while ( ((i+2) < numChars) &&
                             (c=='%')) {
-                        int v = Integer.parseInt(s, i + 1, i + 3, 16);
-                        if (v < 0)
-                            throw new IllegalArgumentException(
-                                    "URLDecoder: Illegal hex characters in escape "
-                                            + "(%) pattern - negative value");
+                        int v = HexFormat.fromHexDigits(s, i + 1, i + 3);
                         bytes[pos++] = (byte) v;
                         i+= 3;
                         if (i < numChars)