001 /*
002 * Copyright 2003-2004 Sun Microsystems, Inc. All Rights Reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation. Sun designates this
008 * particular file as subject to the "Classpath" exception as provided
009 * by Sun in the LICENSE file that accompanied this code.
010 *
011 * This code is distributed in the hope that it will be useful, but WITHOUT
012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014 * version 2 for more details (a copy is included in the LICENSE file that
015 * accompanied this code).
016 *
017 * You should have received a copy of the GNU General Public License version
018 * 2 along with this work; if not, write to the Free Software Foundation,
019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020 *
021 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022 * CA 95054 USA or visit www.sun.com if you need additional information or
023 * have any questions.
024 */
025
026 package java.util;
027
028 import java.io.IOException;
029
030 /**
031 * The <tt>Formattable</tt> interface must be implemented by any class that
032 * needs to perform custom formatting using the <tt>'s'</tt> conversion
033 * specifier of {@link java.util.Formatter}. This interface allows basic
034 * control for formatting arbitrary objects.
035 *
036 * For example, the following class prints out different representations of a
037 * stock's name depending on the flags and length constraints:
038 *
039 * <blockquote><pre>
040 * import java.nio.CharBuffer;
041 * import java.util.Formatter;
042 * import java.util.Formattable;
043 * import java.util.Locale;
044 * import static java.util.FormattableFlags.*;
045 *
046 * ...
047 *
048 * public class StockName implements Formattable {
049 * private String symbol, companyName, frenchCompanyName;
050 * public StockName(String symbol, String companyName,
051 * String frenchCompanyName) {
052 * ...
053 * }
054 *
055 * ...
056 *
057 * public void formatTo(Formatter fmt, int f, int width, int precision) {
058 * StringBuilder sb = new StringBuilder();
059 *
060 * // decide form of name
061 * String name = companyName;
062 * if (fmt.locale().equals(Locale.FRANCE))
063 * name = frenchCompanyName;
064 * boolean alternate = (f & ALTERNATE) == ALTERNATE;
065 * boolean usesymbol = alternate || (precision != -1 && precision < 10);
066 * String out = (usesymbol ? symbol : name);
067 *
068 * // apply precision
069 * if (precision == -1 || out.length() < precision) {
070 * // write it all
071 * sb.append(out);
072 * } else {
073 * sb.append(out.substring(0, precision - 1)).append('*');
074 * }
075 *
076 * // apply width and justification
077 * int len = sb.length();
078 * if (len < width)
079 * for (int i = 0; i < width - len; i++)
080 * if ((f & LEFT_JUSTIFY) == LEFT_JUSTIFY)
081 * sb.append(' ');
082 * else
083 * sb.insert(0, ' ');
084 *
085 * fmt.format(sb.toString());
086 * }
087 *
088 * public String toString() {
089 * return String.format("%s - %s", symbol, companyName);
090 * }
091 * }
092 * </pre></blockquote>
093 *
094 * <p> When used in conjunction with the {@link java.util.Formatter}, the above
095 * class produces the following output for various format strings.
096 *
097 * <blockquote><pre>
098 * Formatter fmt = new Formatter();
099 * StockName sn = new StockName("HUGE", "Huge Fruit, Inc.",
100 * "Fruit Titanesque, Inc.");
101 * fmt.format("%s", sn); // -> "Huge Fruit, Inc."
102 * fmt.format("%s", sn.toString()); // -> "HUGE - Huge Fruit, Inc."
103 * fmt.format("%#s", sn); // -> "HUGE"
104 * fmt.format("%-10.8s", sn); // -> "HUGE "
105 * fmt.format("%.12s", sn); // -> "Huge Fruit,*"
106 * fmt.format(Locale.FRANCE, "%25s", sn); // -> " Fruit Titanesque, Inc."
107 * </pre></blockquote>
108 *
109 * <p> Formattables are not necessarily safe for multithreaded access. Thread
110 * safety is optional and may be enforced by classes that extend and implement
111 * this interface.
112 *
113 * <p> Unless otherwise specified, passing a <tt>null</tt> argument to
114 * any method in this interface will cause a {@link
115 * NullPointerException} to be thrown.
116 *
117 * @version 1.10, 05/05/07
118 * @since 1.5
119 */
120 public interface Formattable {
121
122 /**
123 * Formats the object using the provided {@link Formatter formatter}.
124 *
125 * @param formatter
126 * The {@link Formatter formatter}. Implementing classes may call
127 * {@link Formatter#out() formatter.out()} or {@link
128 * Formatter#locale() formatter.locale()} to obtain the {@link
129 * Appendable} or {@link Locale} used by this
130 * <tt>formatter</tt> respectively.
131 *
132 * @param flags
133 * The flags modify the output format. The value is interpreted as
134 * a bitmask. Any combination of the following flags may be set:
135 * {@link FormattableFlags#LEFT_JUSTIFY}, {@link
136 * FormattableFlags#UPPERCASE}, and {@link
137 * FormattableFlags#ALTERNATE}. If no flags are set, the default
138 * formatting of the implementing class will apply.
139 *
140 * @param width
141 * The minimum number of characters to be written to the output.
142 * If the length of the converted value is less than the
143 * <tt>width</tt> then the output will be padded by
144 * <tt>' '</tt> until the total number of characters
145 * equals width. The padding is at the beginning by default. If
146 * the {@link FormattableFlags#LEFT_JUSTIFY} flag is set then the
147 * padding will be at the end. If <tt>width</tt> is <tt>-1</tt>
148 * then there is no minimum.
149 *
150 * @param precision
151 * The maximum number of characters to be written to the output.
152 * The precision is applied before the width, thus the output will
153 * be truncated to <tt>precision</tt> characters even if the
154 * <tt>width</tt> is greater than the <tt>precision</tt>. If
155 * <tt>precision</tt> is <tt>-1</tt> then there is no explicit
156 * limit on the number of characters.
157 *
158 * @throws IllegalFormatException
159 * If any of the parameters are invalid. For specification of all
160 * possible formatting errors, see the <a
161 * href="../util/Formatter.html#detail">Details</a> section of the
162 * formatter class specification.
163 */
164 void formatTo(Formatter formatter, int flags, int width,
165 int precision);
166 }
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