Here you can find the source of toHexEscape(final int u0)
private static String toHexEscape(final int u0)
//package com.java2s; /*/* w w w .jav a 2 s. c o m*/ * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ public class Main { private static String toHexEscape(final int u0) { int u = u0; int len; final byte[] b = new byte[6]; if (u <= 0x7f) { b[0] = (byte) u; len = 1; } else { // > 0x7ff -> length 2 // > 0xffff -> length 3 // and so on. each new length is an additional 5 bits from the // original 11 // the final mask is 8-len zeros in the low part. len = 2; for (int mask = u >>> 11; mask != 0; mask >>>= 5) { len++; } for (int i = len - 1; i > 0; i--) { b[i] = (byte) (0x80 | (u & 0x3f)); u >>>= 6; // 64 bits per octet. } b[0] = (byte) (~((1 << (8 - len)) - 1) | u); } final StringBuilder sb = new StringBuilder(); for (int i = 0; i < len; i++) { sb.append('%'); if ((b[i] & 0xff) < 0x10) { sb.append('0'); } sb.append(Integer.toHexString(b[i] & 0xff).toUpperCase()); } return sb.toString(); } }