Java tutorial
/* * Copyright (c) 1996, 2019, 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. */ /* * (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved * (C) Copyright IBM Corp. 1996 - 1998 - All Rights Reserved * * The original version of this source code and documentation is copyrighted * and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These * materials are provided under terms of a License Agreement between Taligent * and Sun. This technology is protected by multiple US and International * patents. This notice and attribution to Taligent may not be removed. * Taligent is a registered trademark of Taligent, Inc. * */ package java.text; import java.io.Serializable; /** * <code>Format</code> is an abstract base class for formatting locale-sensitive * information such as dates, messages, and numbers. * * <p> * <code>Format</code> defines the programming interface for formatting * locale-sensitive objects into <code>String</code>s (the * <code>format</code> method) and for parsing <code>String</code>s back * into objects (the <code>parseObject</code> method). * * <p> * Generally, a format's <code>parseObject</code> method must be able to parse * any string formatted by its <code>format</code> method. However, there may * be exceptional cases where this is not possible. For example, a * <code>format</code> method might create two adjacent integer numbers with * no separator in between, and in this case the <code>parseObject</code> could * not tell which digits belong to which number. * * <h2>Subclassing</h2> * * <p> * The Java Platform provides three specialized subclasses of <code>Format</code>-- * <code>DateFormat</code>, <code>MessageFormat</code>, and * <code>NumberFormat</code>--for formatting dates, messages, and numbers, * respectively. * <p> * Concrete subclasses must implement three methods: * <ol> * <li> <code>format(Object obj, StringBuffer toAppendTo, FieldPosition pos)</code> * <li> <code>formatToCharacterIterator(Object obj)</code> * <li> <code>parseObject(String source, ParsePosition pos)</code> * </ol> * These general methods allow polymorphic parsing and formatting of objects * and are used, for example, by <code>MessageFormat</code>. * Subclasses often also provide additional <code>format</code> methods for * specific input types as well as <code>parse</code> methods for specific * result types. Any <code>parse</code> method that does not take a * <code>ParsePosition</code> argument should throw <code>ParseException</code> * when no text in the required format is at the beginning of the input text. * * <p> * Most subclasses will also implement the following factory methods: * <ol> * <li> * <code>getInstance</code> for getting a useful format object appropriate * for the current locale * <li> * <code>getInstance(Locale)</code> for getting a useful format * object appropriate for the specified locale * </ol> * In addition, some subclasses may also implement other * <code>getXxxxInstance</code> methods for more specialized control. For * example, the <code>NumberFormat</code> class provides * <code>getPercentInstance</code> and <code>getCurrencyInstance</code> * methods for getting specialized number formatters. * * <p> * Subclasses of <code>Format</code> that allow programmers to create objects * for locales (with <code>getInstance(Locale)</code> for example) * must also implement the following class method: * <blockquote> * <pre> * public static Locale[] getAvailableLocales() * </pre> * </blockquote> * * <p> * And finally subclasses may define a set of constants to identify the various * fields in the formatted output. These constants are used to create a FieldPosition * object which identifies what information is contained in the field and its * position in the formatted result. These constants should be named * <code><em>item</em>_FIELD</code> where <code><em>item</em></code> identifies * the field. For examples of these constants, see <code>ERA_FIELD</code> and its * friends in {@link DateFormat}. * * <h3><a id="synchronization">Synchronization</a></h3> * * <p> * Formats are generally not synchronized. * It is recommended to create separate format instances for each thread. * If multiple threads access a format concurrently, it must be synchronized * externally. * * @see java.text.ParsePosition * @see java.text.FieldPosition * @see java.text.NumberFormat * @see java.text.DateFormat * @see java.text.MessageFormat * @author Mark Davis * @since 1.1 */ public abstract class Format implements Serializable, Cloneable { private static final long serialVersionUID = -299282585814624189L; /** * Sole constructor. (For invocation by subclass constructors, typically * implicit.) */ protected Format() { } /** * Formats an object to produce a string. This is equivalent to * <blockquote> * {@link #format(Object, StringBuffer, FieldPosition) format}<code>(obj, * new StringBuffer(), new FieldPosition(0)).toString();</code> * </blockquote> * * @param obj The object to format * @return Formatted string. * @exception IllegalArgumentException if the Format cannot format the given * object */ public final String format(Object obj) { return format(obj, new StringBuffer(), new FieldPosition(0)).toString(); } /** * Formats an object and appends the resulting text to a given string * buffer. * If the <code>pos</code> argument identifies a field used by the format, * then its indices are set to the beginning and end of the first such * field encountered. * * @param obj The object to format * @param toAppendTo where the text is to be appended * @param pos A <code>FieldPosition</code> identifying a field * in the formatted text * @return the string buffer passed in as <code>toAppendTo</code>, * with formatted text appended * @exception NullPointerException if <code>toAppendTo</code> or * <code>pos</code> is null * @exception IllegalArgumentException if the Format cannot format the given * object */ public abstract StringBuffer format(Object obj, StringBuffer toAppendTo, FieldPosition pos); /** * Formats an Object producing an <code>AttributedCharacterIterator</code>. * You can use the returned <code>AttributedCharacterIterator</code> * to build the resulting String, as well as to determine information * about the resulting String. * <p> * Each attribute key of the AttributedCharacterIterator will be of type * <code>Field</code>. It is up to each <code>Format</code> implementation * to define what the legal values are for each attribute in the * <code>AttributedCharacterIterator</code>, but typically the attribute * key is also used as the attribute value. * <p>The default implementation creates an * <code>AttributedCharacterIterator</code> with no attributes. Subclasses * that support fields should override this and create an * <code>AttributedCharacterIterator</code> with meaningful attributes. * * @exception NullPointerException if obj is null. * @exception IllegalArgumentException when the Format cannot format the * given object. * @param obj The object to format * @return AttributedCharacterIterator describing the formatted value. * @since 1.4 */ public AttributedCharacterIterator formatToCharacterIterator(Object obj) { return createAttributedCharacterIterator(format(obj)); } /** * Parses text from a string to produce an object. * <p> * The method attempts to parse text starting at the index given by * <code>pos</code>. * If parsing succeeds, then the index of <code>pos</code> is updated * to the index after the last character used (parsing does not necessarily * use all characters up to the end of the string), and the parsed * object is returned. The updated <code>pos</code> can be used to * indicate the starting point for the next call to this method. * If an error occurs, then the index of <code>pos</code> is not * changed, the error index of <code>pos</code> is set to the index of * the character where the error occurred, and null is returned. * * @param source A <code>String</code>, part of which should be parsed. * @param pos A <code>ParsePosition</code> object with index and error * index information as described above. * @return An <code>Object</code> parsed from the string. In case of * error, returns null. * @throws NullPointerException if {@code source} or {@code pos} is null. */ public abstract Object parseObject(String source, ParsePosition pos); /** * Parses text from the beginning of the given string to produce an object. * The method may not use the entire text of the given string. * * @param source A <code>String</code> whose beginning should be parsed. * @return An <code>Object</code> parsed from the string. * @exception ParseException if the beginning of the specified string * cannot be parsed. * @throws NullPointerException if {@code source} is null. */ public Object parseObject(String source) throws ParseException { ParsePosition pos = new ParsePosition(0); Object result = parseObject(source, pos); if (pos.index == 0) { throw new ParseException("Format.parseObject(String) failed", pos.errorIndex); } return result; } /** * Creates and returns a copy of this object. * * @return a clone of this instance. */ public Object clone() { try { return super.clone(); } catch (CloneNotSupportedException e) { // will never happen throw new InternalError(e); } } // // Convenience methods for creating AttributedCharacterIterators from // different parameters. // /** * Creates an <code>AttributedCharacterIterator</code> for the String * <code>s</code>. * * @param s String to create AttributedCharacterIterator from * @return AttributedCharacterIterator wrapping s */ AttributedCharacterIterator createAttributedCharacterIterator(String s) { AttributedString as = new AttributedString(s); return as.getIterator(); } /** * Creates an <code>AttributedCharacterIterator</code> containing the * concatenated contents of the passed in * <code>AttributedCharacterIterator</code>s. * * @param iterators AttributedCharacterIterators used to create resulting * AttributedCharacterIterators * @return AttributedCharacterIterator wrapping passed in * AttributedCharacterIterators */ AttributedCharacterIterator createAttributedCharacterIterator(AttributedCharacterIterator[] iterators) { AttributedString as = new AttributedString(iterators); return as.getIterator(); } /** * Returns an AttributedCharacterIterator with the String * <code>string</code> and additional key/value pair <code>key</code>, * <code>value</code>. * * @param string String to create AttributedCharacterIterator from * @param key Key for AttributedCharacterIterator * @param value Value associated with key in AttributedCharacterIterator * @return AttributedCharacterIterator wrapping args */ AttributedCharacterIterator createAttributedCharacterIterator(String string, AttributedCharacterIterator.Attribute key, Object value) { AttributedString as = new AttributedString(string); as.addAttribute(key, value); return as.getIterator(); } /** * Creates an AttributedCharacterIterator with the contents of * <code>iterator</code> and the additional attribute <code>key</code> * <code>value</code>. * * @param iterator Initial AttributedCharacterIterator to add arg to * @param key Key for AttributedCharacterIterator * @param value Value associated with key in AttributedCharacterIterator * @return AttributedCharacterIterator wrapping args */ AttributedCharacterIterator createAttributedCharacterIterator(AttributedCharacterIterator iterator, AttributedCharacterIterator.Attribute key, Object value) { AttributedString as = new AttributedString(iterator); as.addAttribute(key, value); return as.getIterator(); } /** * Defines constants that are used as attribute keys in the * <code>AttributedCharacterIterator</code> returned * from <code>Format.formatToCharacterIterator</code> and as * field identifiers in <code>FieldPosition</code>. * * @since 1.4 */ public static class Field extends AttributedCharacterIterator.Attribute { // Proclaim serial compatibility with 1.4 FCS private static final long serialVersionUID = 276966692217360283L; /** * Creates a Field with the specified name. * * @param name Name of the attribute */ protected Field(String name) { super(name); } } /** * FieldDelegate is notified by the various <code>Format</code> * implementations as they are formatting the Objects. This allows for * storage of the individual sections of the formatted String for * later use, such as in a <code>FieldPosition</code> or for an * <code>AttributedCharacterIterator</code>. * <p> * Delegates should NOT assume that the <code>Format</code> will notify * the delegate of fields in any particular order. * * @see FieldPosition#getFieldDelegate * @see CharacterIteratorFieldDelegate */ interface FieldDelegate { /** * Notified when a particular region of the String is formatted. This * method will be invoked if there is no corresponding integer field id * matching <code>attr</code>. * * @param attr Identifies the field matched * @param value Value associated with the field * @param start Beginning location of the field, will be >= 0 * @param end End of the field, will be >= start and <= buffer.length() * @param buffer Contains current formatted value, receiver should * NOT modify it. */ public void formatted(Format.Field attr, Object value, int start, int end, StringBuffer buffer); /** * Notified when a particular region of the String is formatted. * * @param fieldID Identifies the field by integer * @param attr Identifies the field matched * @param value Value associated with the field * @param start Beginning location of the field, will be >= 0 * @param end End of the field, will be >= start and <= buffer.length() * @param buffer Contains current formatted value, receiver should * NOT modify it. */ public void formatted(int fieldID, Format.Field attr, Object value, int start, int end, StringBuffer buffer); } }