Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.apache.commons.text.translate; import java.io.IOException; import java.io.StringWriter; import java.io.Writer; import java.util.Locale; /** * An API for translating text. * Its core use is to escape and unescape text. Because escaping and unescaping * is completely contextual, the API does not present two separate signatures. * * @since 1.0 */ public abstract class CharSequenceTranslator { static final char[] HEX_DIGITS = new char[] { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' }; /** * Translate a set of codepoints, represented by an int index into a CharSequence, * into another set of codepoints. The number of codepoints consumed must be returned, * and the only IOExceptions thrown must be from interacting with the Writer so that * the top level API may reliably ignore StringWriter IOExceptions. * * @param input CharSequence that is being translated * @param index int representing the current point of translation * @param out Writer to translate the text to * @return int count of codepoints consumed * @throws IOException if and only if the Writer produces an IOException */ public abstract int translate(CharSequence input, int index, Writer out) throws IOException; /** * Helper for non-Writer usage. * @param input CharSequence to be translated * @return String output of translation */ public final String translate(final CharSequence input) { if (input == null) { return null; } try { final StringWriter writer = new StringWriter(input.length() * 2); translate(input, writer); return writer.toString(); } catch (final IOException ioe) { // this should never ever happen while writing to a StringWriter throw new RuntimeException(ioe); } } /** * Translate an input onto a Writer. This is intentionally final as its algorithm is * tightly coupled with the abstract method of this class. * * @param input CharSequence that is being translated * @param out Writer to translate the text to * @throws IOException if and only if the Writer produces an IOException */ public final void translate(final CharSequence input, final Writer out) throws IOException { if (out == null) { throw new IllegalArgumentException("The Writer must not be null"); } if (input == null) { return; } int pos = 0; final int len = input.length(); while (pos < len) { final int consumed = translate(input, pos, out); if (consumed == 0) { // inlined implementation of Character.toChars(Character.codePointAt(input, pos)) // avoids allocating temp char arrays and duplicate checks final char c1 = input.charAt(pos); out.write(c1); pos++; if (Character.isHighSurrogate(c1) && pos < len) { final char c2 = input.charAt(pos); if (Character.isLowSurrogate(c2)) { out.write(c2); pos++; } } continue; } // contract with translators is that they have to understand codepoints // and they just took care of a surrogate pair for (int pt = 0; pt < consumed; pt++) { pos += Character.charCount(Character.codePointAt(input, pos)); } } } /** * Helper method to create a merger of this translator with another set of * translators. Useful in customizing the standard functionality. * * @param translators CharSequenceTranslator array of translators to merge with this one * @return CharSequenceTranslator merging this translator with the others */ public final CharSequenceTranslator with(final CharSequenceTranslator... translators) { final CharSequenceTranslator[] newArray = new CharSequenceTranslator[translators.length + 1]; newArray[0] = this; System.arraycopy(translators, 0, newArray, 1, translators.length); return new AggregateTranslator(newArray); } /** * <p>Returns an upper case hexadecimal <code>String</code> for the given * character.</p> * * @param codepoint The codepoint to convert. * @return An upper case hexadecimal <code>String</code> */ public static String hex(final int codepoint) { return Integer.toHexString(codepoint).toUpperCase(Locale.ENGLISH); } }