J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2003-2004 Sun Microsystems, Inc. All Rights Reserved. |
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 4 | * |
| 5 | * This code is free software; you can redistribute it and/or modify it |
| 6 | * under the terms of the GNU General Public License version 2 only, as |
| 7 | * published by the Free Software Foundation. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun in the LICENSE file that accompanied this code. |
| 10 | * |
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT |
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 14 | * version 2 for more details (a copy is included in the LICENSE file that |
| 15 | * accompanied this code). |
| 16 | * |
| 17 | * You should have received a copy of the GNU General Public License version |
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, |
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| 20 | * |
| 21 | * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any questions. |
| 24 | */ |
| 25 | |
| 26 | package java.util; |
| 27 | |
| 28 | import java.io.IOException; |
| 29 | |
| 30 | /** |
| 31 | * The <tt>Formattable</tt> interface must be implemented by any class that |
| 32 | * needs to perform custom formatting using the <tt>'s'</tt> conversion |
| 33 | * specifier of {@link java.util.Formatter}. This interface allows basic |
| 34 | * control for formatting arbitrary objects. |
| 35 | * |
| 36 | * For example, the following class prints out different representations of a |
| 37 | * stock's name depending on the flags and length constraints: |
| 38 | * |
| 39 | * <blockquote><pre> |
| 40 | * import java.nio.CharBuffer; |
| 41 | * import java.util.Formatter; |
| 42 | * import java.util.Formattable; |
| 43 | * import java.util.Locale; |
| 44 | * import static java.util.FormattableFlags.*; |
| 45 | * |
| 46 | * ... |
| 47 | * |
| 48 | * public class StockName implements Formattable { |
| 49 | * private String symbol, companyName, frenchCompanyName; |
| 50 | * public StockName(String symbol, String companyName, |
| 51 | * String frenchCompanyName) { |
| 52 | * ... |
| 53 | * } |
| 54 | * |
| 55 | * ... |
| 56 | * |
| 57 | * public void formatTo(Formatter fmt, int f, int width, int precision) { |
| 58 | * StringBuilder sb = new StringBuilder(); |
| 59 | * |
| 60 | * // decide form of name |
| 61 | * String name = companyName; |
| 62 | * if (fmt.locale().equals(Locale.FRANCE)) |
| 63 | * name = frenchCompanyName; |
| 64 | * boolean alternate = (f & ALTERNATE) == ALTERNATE; |
| 65 | * boolean usesymbol = alternate || (precision != -1 && precision < 10); |
| 66 | * String out = (usesymbol ? symbol : name); |
| 67 | * |
| 68 | * // apply precision |
| 69 | * if (precision == -1 || out.length() < precision) { |
| 70 | * // write it all |
| 71 | * sb.append(out); |
| 72 | * } else { |
| 73 | * sb.append(out.substring(0, precision - 1)).append('*'); |
| 74 | * } |
| 75 | * |
| 76 | * // apply width and justification |
| 77 | * int len = sb.length(); |
| 78 | * if (len < width) |
| 79 | * for (int i = 0; i < width - len; i++) |
| 80 | * if ((f & LEFT_JUSTIFY) == LEFT_JUSTIFY) |
| 81 | * sb.append(' '); |
| 82 | * else |
| 83 | * sb.insert(0, ' '); |
| 84 | * |
| 85 | * fmt.format(sb.toString()); |
| 86 | * } |
| 87 | * |
| 88 | * public String toString() { |
| 89 | * return String.format("%s - %s", symbol, companyName); |
| 90 | * } |
| 91 | * } |
| 92 | * </pre></blockquote> |
| 93 | * |
| 94 | * <p> When used in conjunction with the {@link java.util.Formatter}, the above |
| 95 | * class produces the following output for various format strings. |
| 96 | * |
| 97 | * <blockquote><pre> |
| 98 | * Formatter fmt = new Formatter(); |
| 99 | * 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 | * @since 1.5 |
| 118 | */ |
| 119 | public interface Formattable { |
| 120 | |
| 121 | /** |
| 122 | * Formats the object using the provided {@link Formatter formatter}. |
| 123 | * |
| 124 | * @param formatter |
| 125 | * The {@link Formatter formatter}. Implementing classes may call |
| 126 | * {@link Formatter#out() formatter.out()} or {@link |
| 127 | * Formatter#locale() formatter.locale()} to obtain the {@link |
| 128 | * Appendable} or {@link Locale} used by this |
| 129 | * <tt>formatter</tt> respectively. |
| 130 | * |
| 131 | * @param flags |
| 132 | * The flags modify the output format. The value is interpreted as |
| 133 | * a bitmask. Any combination of the following flags may be set: |
| 134 | * {@link FormattableFlags#LEFT_JUSTIFY}, {@link |
| 135 | * FormattableFlags#UPPERCASE}, and {@link |
| 136 | * FormattableFlags#ALTERNATE}. If no flags are set, the default |
| 137 | * formatting of the implementing class will apply. |
| 138 | * |
| 139 | * @param width |
| 140 | * The minimum number of characters to be written to the output. |
| 141 | * If the length of the converted value is less than the |
| 142 | * <tt>width</tt> then the output will be padded by |
| 143 | * <tt>' '</tt> until the total number of characters |
| 144 | * equals width. The padding is at the beginning by default. If |
| 145 | * the {@link FormattableFlags#LEFT_JUSTIFY} flag is set then the |
| 146 | * padding will be at the end. If <tt>width</tt> is <tt>-1</tt> |
| 147 | * then there is no minimum. |
| 148 | * |
| 149 | * @param precision |
| 150 | * The maximum number of characters to be written to the output. |
| 151 | * The precision is applied before the width, thus the output will |
| 152 | * be truncated to <tt>precision</tt> characters even if the |
| 153 | * <tt>width</tt> is greater than the <tt>precision</tt>. If |
| 154 | * <tt>precision</tt> is <tt>-1</tt> then there is no explicit |
| 155 | * limit on the number of characters. |
| 156 | * |
| 157 | * @throws IllegalFormatException |
| 158 | * If any of the parameters are invalid. For specification of all |
| 159 | * possible formatting errors, see the <a |
| 160 | * href="../util/Formatter.html#detail">Details</a> section of the |
| 161 | * formatter class specification. |
| 162 | */ |
| 163 | void formatTo(Formatter formatter, int flags, int width, int precision); |
| 164 | } |