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/*
* Copyright (c) 2003, 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.
*/
package java.util;
import java.io.IOException;
/**
* The <tt>Formattable</tt> interface must be implemented by any class that
* needs to perform custom formatting using the <tt>'s'</tt> conversion
* specifier of {@link java.util.Formatter}. This interface allows basic
* control for formatting arbitrary objects.
*
* For example, the following class prints out different representations of a
* stock's name depending on the flags and length constraints:
*
* <pre> {@code
* import java.nio.CharBuffer;
* import java.util.Formatter;
* import java.util.Formattable;
* import java.util.Locale;
* import static java.util.FormattableFlags.*;
*
* ...
*
* public class StockName implements Formattable {
* private String symbol, companyName, frenchCompanyName;
* public StockName(String symbol, String companyName,
* String frenchCompanyName) {
* ...
* }
*
* ...
*
* public void formatTo(Formatter fmt, int f, int width, int precision) {
* StringBuilder sb = new StringBuilder();
*
* // decide form of name
* String name = companyName;
* if (fmt.locale().equals(Locale.FRANCE))
* name = frenchCompanyName;
* boolean alternate = (f & ALTERNATE) == ALTERNATE;
* boolean usesymbol = alternate || (precision != -1 && precision < 10);
* String out = (usesymbol ? symbol : name);
*
* // apply precision
* if (precision == -1 || out.length() < precision) {
* // write it all
* sb.append(out);
* } else {
* sb.append(out.substring(0, precision - 1)).append('*');
* }
*
* // apply width and justification
* int len = sb.length();
* if (len < width)
* for (int i = 0; i < width - len; i++)
* if ((f & LEFT_JUSTIFY) == LEFT_JUSTIFY)
* sb.append(' ');
* else
* sb.insert(0, ' ');
*
* fmt.format(sb.toString());
* }
*
* public String toString() {
* return String.format("%s - %s", symbol, companyName);
* }
* }
* }</pre>
*
* <p> When used in conjunction with the {@link java.util.Formatter}, the above
* class produces the following output for various format strings.
*
* <pre> {@code
* Formatter fmt = new Formatter();
* StockName sn = new StockName("HUGE", "Huge Fruit, Inc.",
* "Fruit Titanesque, Inc.");
* fmt.format("%s", sn); // -> "Huge Fruit, Inc."
* fmt.format("%s", sn.toString()); // -> "HUGE - Huge Fruit, Inc."
* fmt.format("%#s", sn); // -> "HUGE"
* fmt.format("%-10.8s", sn); // -> "HUGE "
* fmt.format("%.12s", sn); // -> "Huge Fruit,*"
* fmt.format(Locale.FRANCE, "%25s", sn); // -> " Fruit Titanesque, Inc."
* }</pre>
*
* <p> Formattables are not necessarily safe for multithreaded access. Thread
* safety is optional and may be enforced by classes that extend and implement
* this interface.
*
* <p> Unless otherwise specified, passing a <tt>null</tt> argument to
* any method in this interface will cause a {@link
* NullPointerException} to be thrown.
*
* @since 1.5
*/
public interface Formattable {
/**
* Formats the object using the provided {@link Formatter formatter}.
*
* @param formatter
* The {@link Formatter formatter}. Implementing classes may call
* {@link Formatter#out() formatter.out()} or {@link
* Formatter#locale() formatter.locale()} to obtain the {@link
* Appendable} or {@link Locale} used by this
* <tt>formatter</tt> respectively.
*
* @param flags
* The flags modify the output format. The value is interpreted as
* a bitmask. Any combination of the following flags may be set:
* {@link FormattableFlags#LEFT_JUSTIFY}, {@link
* FormattableFlags#UPPERCASE}, and {@link
* FormattableFlags#ALTERNATE}. If no flags are set, the default
* formatting of the implementing class will apply.
*
* @param width
* The minimum number of characters to be written to the output.
* If the length of the converted value is less than the
* <tt>width</tt> then the output will be padded by
* <tt>' '</tt> until the total number of characters
* equals width. The padding is at the beginning by default. If
* the {@link FormattableFlags#LEFT_JUSTIFY} flag is set then the
* padding will be at the end. If <tt>width</tt> is <tt>-1</tt>
* then there is no minimum.
*
* @param precision
* The maximum number of characters to be written to the output.
* The precision is applied before the width, thus the output will
* be truncated to <tt>precision</tt> characters even if the
* <tt>width</tt> is greater than the <tt>precision</tt>. If
* <tt>precision</tt> is <tt>-1</tt> then there is no explicit
* limit on the number of characters.
*
* @throws IllegalFormatException
* If any of the parameters are invalid. For specification of all
* possible formatting errors, see the <a
* href="../util/Formatter.html#detail">Details</a> section of the
* formatter class specification.
*/
void formatTo(Formatter formatter, int flags, int width, int precision);
}
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