165 lines
6.8 KiB
Java
165 lines
6.8 KiB
Java
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/*
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* Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.util;
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import java.io.IOException;
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/**
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* The {@code Formattable} interface must be implemented by any class that
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* needs to perform custom formatting using the {@code 's'} conversion
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* specifier of {@link java.util.Formatter}. This interface allows basic
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* control for formatting arbitrary objects.
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*
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* For example, the following class prints out different representations of a
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* stock's name depending on the flags and length constraints:
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*
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* <pre> {@code
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* import java.nio.CharBuffer;
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* import java.util.Formatter;
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* import java.util.Formattable;
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* import java.util.Locale;
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* import static java.util.FormattableFlags.*;
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*
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* ...
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*
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* public class StockName implements Formattable {
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* private String symbol, companyName, frenchCompanyName;
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* public StockName(String symbol, String companyName,
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* String frenchCompanyName) {
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* ...
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* }
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*
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* ...
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*
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* public void formatTo(Formatter fmt, int f, int width, int precision) {
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* StringBuilder sb = new StringBuilder();
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*
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* // decide form of name
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* String name = companyName;
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* if (fmt.locale().equals(Locale.FRANCE))
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* name = frenchCompanyName;
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* boolean alternate = (f & ALTERNATE) == ALTERNATE;
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* boolean usesymbol = alternate || (precision != -1 && precision < 10);
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* String out = (usesymbol ? symbol : name);
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*
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* // apply precision
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* if (precision == -1 || out.length() < precision) {
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* // write it all
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* sb.append(out);
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* } else {
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* sb.append(out.substring(0, precision - 1)).append('*');
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* }
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*
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* // apply width and justification
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* int len = sb.length();
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* if (len < width)
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* for (int i = 0; i < width - len; i++)
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* if ((f & LEFT_JUSTIFY) == LEFT_JUSTIFY)
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* sb.append(' ');
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* else
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* sb.insert(0, ' ');
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*
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* fmt.format(sb.toString());
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* }
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*
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* public String toString() {
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* return String.format("%s - %s", symbol, companyName);
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* }
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* }
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* }</pre>
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*
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* <p> When used in conjunction with the {@link java.util.Formatter}, the above
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* class produces the following output for various format strings.
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*
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* <pre> {@code
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* Formatter fmt = new Formatter();
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* StockName sn = new StockName("HUGE", "Huge Fruit, Inc.",
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* "Fruit Titanesque, Inc.");
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* fmt.format("%s", sn); // -> "Huge Fruit, Inc."
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* fmt.format("%s", sn.toString()); // -> "HUGE - Huge Fruit, Inc."
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* fmt.format("%#s", sn); // -> "HUGE"
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* fmt.format("%-10.8s", sn); // -> "HUGE "
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* fmt.format("%.12s", sn); // -> "Huge Fruit,*"
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* fmt.format(Locale.FRANCE, "%25s", sn); // -> " Fruit Titanesque, Inc."
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* }</pre>
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*
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* <p> Formattables are not necessarily safe for multithreaded access. Thread
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* safety is optional and may be enforced by classes that extend and implement
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* this interface.
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*
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* <p> Unless otherwise specified, passing a {@code null} argument to
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* any method in this interface will cause a {@link
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* NullPointerException} to be thrown.
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*
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* @since 1.5
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*/
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public interface Formattable {
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/**
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* Formats the object using the provided {@link Formatter formatter}.
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*
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* @param formatter
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* The {@link Formatter formatter}. Implementing classes may call
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* {@link Formatter#out() formatter.out()} or {@link
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* Formatter#locale() formatter.locale()} to obtain the {@link
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* Appendable} or {@link Locale} used by this
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* {@code formatter} respectively.
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*
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* @param flags
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* The flags modify the output format. The value is interpreted as
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* a bitmask. Any combination of the following flags may be set:
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* {@link FormattableFlags#LEFT_JUSTIFY}, {@link
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* FormattableFlags#UPPERCASE}, and {@link
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* FormattableFlags#ALTERNATE}. If no flags are set, the default
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* formatting of the implementing class will apply.
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*
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* @param width
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* The minimum number of characters to be written to the output.
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* If the length of the converted value is less than the
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* {@code width} then the output will be padded by
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* <code>' '</code> until the total number of characters
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* equals width. The padding is at the beginning by default. If
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* the {@link FormattableFlags#LEFT_JUSTIFY} flag is set then the
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* padding will be at the end. If {@code width} is {@code -1}
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* then there is no minimum.
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*
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* @param precision
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* The maximum number of characters to be written to the output.
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* The precision is applied before the width, thus the output will
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* be truncated to {@code precision} characters even if the
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* {@code width} is greater than the {@code precision}. If
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* {@code precision} is {@code -1} then there is no explicit
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* limit on the number of characters.
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*
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* @throws IllegalFormatException
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* If any of the parameters are invalid. For specification of all
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* possible formatting errors, see the <a
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* href="../util/Formatter.html#detail">Details</a> section of the
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* formatter class specification.
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*/
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void formatTo(Formatter formatter, int flags, int width, int precision);
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}
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